The sha1sum of a file may update the access time of that file.
If this happens while a brick is down, as it is forced in the
test, that brick doesn't get the update, getting out of sync.

When the brick is restarted, self-heal repairs the file, but
the test shouldn't access brick contents until self-heal finishes.
If this is combined with a kill of another brick before self-heal
has finished repairing the file, the volume could become inaccessible.

Since the purpose of these tests is only to check ec functionality
(there is another test that checks self-heal), the test that corrupts
the file has been removed.

Additional checks to validate the state of the volume have been added
to avoid some timing issues.

This is a backport of http://review.gluster.org/8892/

BUG: 1149118
Change-Id: I8a40b7f07fc8ecd2c721bad1bcdd351dd8504155
Signed-off-by: Xavier Hernandez <xhernandez@datalab.es>
Reviewed-on: http://review.gluster.org/8902
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Dan Lambright <dlambrig@redhat.com>

Some operations, specially those comming from NFS, do not use a
regular fd and use an anonymous fd (i.e. a previous open call has
not been sent). Any context information created during open or
create will not be present on these fd's, so we simply return NULL
for contexts of those fd.

Also it seems that NFS can send write requests with a very big
buffer (higher that the default value of 128 KB). Some changes
have been made to correctly handle these large buffers.

This is a backport of http://review.gluster.org/8367.

Change-Id: I281476bd0d2cbaad231822248d6a616fcf5d4003
BUG: 1126734
Signed-off-by: Xavier Hernandez <xhernandez@datalab.es>
Reviewed-on: http://review.gluster.org/8367
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/8416