LU-2524 test: Modify tdir to be single directory

LU-2524 test: Modify tdir to be single directory

Currently, the tdir variable is a directory with a subdirectory.
This requires the '-p' option when calling mkdir. We've made tdir
be a single directory so calls to mkdir and test_mkdir do not
require the '-p' option in most cases.

tdir was changed from d0.${TESTSUITE}/d${base} to
d${testnum}.${TESTSUITE} and tfile was changed from
f.${TESTSUITE}.${testnum} to f${testnum}.${TESTSUITE}. Now tdir and
tfile are consistent in their format and the call to remove files
and directories at the beginning of many test scripts will remove
these files and directories.

Once this patch lands, we can remove the "-p" option from many
of the calls to mkdir.

Lustre-commit: a98d44e0439ad5b20d0d7f273b29e6ea990312f0
Lustre-change: http://review.whamcloud.com/8123

LU-2524 tests: run sanity test_51ba in test_51b dir

Run the test_51ba directory cleanup in the same directory as the
test_51b subtest created its subdirectories.

Lustre-commit: 47c581b8155f865ade5c9d067f85930146361c2a
Lustre-change: http://review.whamcloud.com/9021

Signed-off-by: James Nunez <james.a.nunez@intel.com>
Change-Id: Ib49d7102a49ff6b5f3ec539a5b2f2f5186231a04
Reviewed-on: http://review.whamcloud.com/8123
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: wangdi <di.wang@intel.com>
Reviewed-on: http://review.whamcloud.com/10349
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>