[Testfix] Modify test to work with new performance.io-cache default

Problem:
The default value of performance.io-cache was ON by default
before gluster 6.0, in gluster 6.0 it was set to OFF.

Solution:
Adding code to check gluster version and then check
weather it is ON or OFF as shown below:
```
        if get_gluster_version(self.mnode) >= 6.0:
            self.assertIn("off", ret['performance.io-cache'],
                          "io-cache value is not correct")
        else:
            self.assertIn("on", ret['performance.io-cache'],
                          "io-cache value is not correct")
```

CentOS-CI failure analysis:
This patch is expected to failed as if we run `gluster --version` on
nightly builds the output returned as shown below:
```
# gluster --version
glusterfs 20200220.a0e0890
Repository revision: git://git.gluster.org/glusterfs.git
Copyright (c) 2006-2016 Red Hat, Inc. <https://www.gluster.org/>
GlusterFS comes with ABSOLUTELY NO WARRANTY.
It is licensed to you under your choice of the GNU Lesser
General Public License, version 3 or any later version (LGPLv3
or later), or the GNU General Public License, version 2 (GPLv2),
in all cases as published by the Free Software Foundation.
```
This output can't be parsed by get_gluster_version() function
which is used in this patch to get the gluster version
and check for perfromance.io-cache's default value accordingly.


Change-Id: I00b652a9d5747cbf3006825bb17b9ca2f69cb9cd
Signed-off-by: kshithijiyer <kshithij.ki@gmail.com>

0 files changed, 0 insertions, 0 deletions