GlusterFS: Renaming test case to test_mount_glusterfs
With the patch [1], GlusterFS is now using mount method in
RemoteFsClient. That method mounts a gluster share only if it has
not already been mounted.
So, having test case name as
test_mount_glusterfs_should_mount_correctly, doesn't make sense now.
This patch changes its name to 'test_mount_glusterfs'.