LU-2711 tests: conf-sanity clean up environment in test

LU-2711 tests: conf-sanity clean up environment in test

Several Lustre test suites execute code or set variables
between tests even if the preceding test is not executed.
In the case of conf-sanity, the code between tests 23a and
23b and between 43b and 44 are there to clean up the environment
from the previous test. Properly clean up the file system
configuration/environment at the end of test 23a and 43b.

Test-Parameters: trivial testlist=conf-sanity

Signed-off-by: James Nunez <james.a.nunez@intel.com>
Change-Id: I250bb2067d0c966f866b404025dc6240b16f301e
Reviewed-on: https://review.whamcloud.com/30703
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Saurabh Tandan <saurabh.tandan@intel.com>
Reviewed-by: Wei Liu <wei3.liu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>