LU-5759 tests: use lfs getstripe -M instead of get_mds_num

LU-5759 tests: use lfs getstripe -M instead of get_mds_num

The get_mds_num() helper function returned the MDS facet number,
but now that can be done via "lfs getdirstripe -M".

Remove this function and fix the few callers to use
"lfs getstripe -M" and create test directory with -c1
flag to prevent directory striping.

Fix some coding style issues in the affected functions.

Test-Parameters: alwaysuploadlogs \
envdefinitions=SLOW=yes,ENABLE_QUOTA=yes \
mdtfilesystemtype=ldiskfs mdsfilesystemtype=ldiskfs \
ostfilesystemtype=ldiskfs mdtcount=1 testlist=replay-dual

Test-Parameters: alwaysuploadlogs \
envdefinitions=SLOW=yes,ENABLE_QUOTA=yes \
mdtfilesystemtype=ldiskfs mdsfilesystemtype=ldiskfs \
ostfilesystemtype=ldiskfs mdtcount=1 testlist=sanity

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Mikhail Pershin <mike.pershin@intel.com>
Change-Id: I35d2ad5d859190c0292d3cc09df23fec40165751
Reviewed-on: http://review.whamcloud.com/12363
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Jian Yu <jian.yu@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>