LU-8885 tests: zconf_mount_clients() defect

LU-8885 tests: zconf_mount_clients() defect

Presently zconf_mount_clients() returns success(0)
in cases where the 'NFS' mount is already mounted
on a mount point which it is trying to mount again.
In this case, it silently ignores the mount, leading
to testcase failure. This patch addresses this defect
by allowing zconf_mount_clients() to compare that
nothing unexpected is mounted by comparing the result
of mount count with mount count of "type lustre". If
they are unequal the function exists with an error.

Lustre-change: https://review.whamcloud.com/24054
Lustre-commit: 10ec9eba801dc80f1ccb9f8fbcbd4b0258940623

Test-Parameters: envdefinitions=PARALLEL_SCALE_EXCEPT=parallel_grouplock \
testlist=sanity,parallel-scale,parallel-scale-nfsv3
Signed-off-by: Arshad Hussain <arshad.hussain@seagate.com>
Change-Id: I55e4b2ef2a18985be4833fca017cc6c6b0c5410f
Seagate-bug-id: MRP-3773
Reviewed-by: Ashish Purkar <ashish.purkar@seagate.com>
Reviewed-by: Ujjwal Lanjewar <ujjwal.lanjewar@seagate.com>
Reviewed-by: Elena V. Gryaznova <elena.gryaznova@seagate.com>
Reviewed-by: Elena Gryaznova <elena.gryaznova@seagate.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/28222
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>