[Libfix] Remove rpyc_get_connection() dependency from code

Problem:
`g.rpyc_get_connection()` has a limitaion where it can't
convert python2 calls to python3 calls. Due to this a large
number of testcases fail when executed from a python2 machine
on a python3 only setup or visa versa with the below stack trace:
```
E  ========= Remote Traceback (1) =========
E  Traceback (most recent call last):
E  File "/root/tmp.tL8Eqx7d8l/rpyc/core/protocol.py", line 323, in _dispatch_request
E       res = self._HANDLERS[handler](self, *args)
E  File "/root/tmp.tL8Eqx7d8l/rpyc/core/protocol.py", line 591, in _handle_inspect
E       if hasattr(self._local_objects[id_pack], '____conn__'):
E  File "/root/tmp.tL8Eqx7d8l/rpyc/lib/colls.py", line 110, in __getitem__
E       return self._dict[key][0]
E  KeyError: (b'rpyc.core.service.SlaveService', 94282642994712, 140067150858560)
```

Solution:
The solution here is to modify the code to not use
`g.rpyc_get_connection()`. The following changes are done
to accomplish it:
1)Remove code which uses g.rpyc_get_connection() and use generic
logic in functions:
 a. do_bricks_exist_in_shd_volfile()
 b. get_disk_usage()
 c. mount_volume()
 d. list_files()
 f. append_string_to_file()
2)Create files which can be uploaded and executed on
clients/servers to avoid rpc calls in functions:
 a. calculate_hash()
 b. validate_files_in_dir()
3)Modify setup.py to push the below files to
`/usr/share/glustolibs/scripts/`:
 a.compute_hash.py
 b.walk_dir.py

Change-Id: I00a81a88382bf3f8b366753eebdb2999260788ca
Signed-off-by: kshithijiyer <kshithij.ki@gmail.com>

1 files changed, 33 insertions, 16 deletions

diff --git a/glustolibs-gluster/glustolibs/gluster/glusterfile.py b/glustolibs-gluster/glustolibs/gluster/glusterfile.py
index 413a4f9a7..4d712a5f3 100755
--- a/glustolibs-gluster/glustolibs/gluster/glusterfile.py
+++ b/glustolibs-gluster/glustolibs/gluster/glusterfile.py
@@ -1,5 +1,5 @@
 #!/usr/bin/env python
-#  Copyright (C) 2018 Red Hat, Inc. <http://www.redhat.com>
+#  Copyright (C) 2018-2020 Red Hat, Inc. <http://www.redhat.com>
 #
 #  This program is free software; you can redistribute it and/or modify
 #  it under the terms of the GNU General Public License as published by
@@ -27,8 +27,8 @@ import os
 import re
 
 from glusto.core import Glusto as g
-
 from glustolibs.gluster.layout import Layout
+from glustolibs.misc.misc_libs import upload_scripts
 
 
 def calculate_hash(host, filename):
@@ -39,26 +39,43 @@ def calculate_hash(host, filename):
 
     Returns:
         An integer representation of the hash
+
+    TODO: For testcases specifically testing hashing routine
+          consider using a baseline external Davies-Meyer hash_value.c
+          Creating comparison hash from same library we are testing
+          may not be best practice here. (Holloway)
     """
-    # TODO: For testcases specifically testing hashing routine
-    #        consider using a baseline external Davies-Meyer hash_value.c
-    #        Creating comparison hash from same library we are testing
-    #        may not be best practice here. (Holloway)
     try:
         # Check if libglusterfs.so.0 is available locally
         glusterfs = ctypes.cdll.LoadLibrary("libglusterfs.so.0")
         g.log.debug("Library libglusterfs.so.0 loaded locally")
+        computed_hash = (
+            ctypes.c_uint32(glusterfs.gf_dm_hashfn(filename,
+                                                   len(filename))))
+        hash_value = int(computed_hash.value)
     except OSError:
-        conn = g.rpyc_get_connection(host)
-        glusterfs = \
-            conn.modules.ctypes.cdll.LoadLibrary("libglusterfs.so.0")
-        g.log.debug("Library libglusterfs.so.0 loaded via rpyc")
-
-    computed_hash = \
-        ctypes.c_uint32(glusterfs.gf_dm_hashfn(filename, len(filename)))
-    # conn.close()
-
-    return int(computed_hash.value)
+        script_path = ("/usr/share/glustolibs/scripts/"
+                       "compute_hash.py")
+        if not file_exists(host, script_path):
+            if upload_scripts(host, script_path,
+                              '/usr/share/glustolibs/scripts/'):
+                g.log.info("Successfully uploaded script "
+                           "compute_hash.py!")
+            else:
+                g.log.error('Unable to upload the script to node {0}'
+                            .format(host))
+                return 0
+        else:
+            g.log.info("compute_hash.py already present!")
+        cmd = ("/usr/bin/env python {0} {1}".format(script_path,
+                                                    filename))
+        ret, out, _ = g.run(host, cmd)
+        if ret:
+            g.log.error('Unable to run the script on node {0}'
+                        .format(host))
+            return 0
+        hash_value = int(out.split('\n')[0])
+    return hash_value
 
 
 def get_mountpoint(host, fqpath):