LU-11010 tests: remove calls to return after skip()

LU-11010 tests: remove calls to return after skip()

The skip() routine now contains a call to exit. All calls
to skip() and skip_env() should be reviewed and calls to
return that follow skip() should be removed.

This is the fourth patch in a series that removes calls
to return after skip() in the Lustre test suites.

Calls to return after skip() are removed for:
mmp.sh
ost-pools.sh
parallel-scale-cifs.sh
parallel-scale-nfs.sh
posix.sh

Test-Parameters: trivial testlist=mmp
Test-Parameters: ostcount=1 osscount=1 testlist=ost-pools
Test-Parameters: mdtfilesystemtype=zfs testlist=posix,mmp
Signed-off-by: James Nunez <james.a.nunez@intel.com>
Change-Id: Ib6e4c81069b142652a0c50c339683dca21f03199
Reviewed-on: https://review.whamcloud.com/32733
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Quentin Bouget <quentin.bouget@cea.fr>
Reviewed-by: Oleg Drokin <green@whamcloud.com>