LU-11597 tests: skip sanityn tests for PPC

LU-11597 tests: skip sanityn tests for PPC

Several sanityn test suite tests fail consistenly when
testing PPC clients.  These tests should be skipped,
added to the ALWAYS_EXCEPT list, until the failures are
understood and fixed.

Tests to skip in sanityn are
16a (LU-11597)
71a (LU-11787)

Lustre-change: https://review.whamcloud.com/37561
Lustre-commit: c27e5fe50ca3de4c9d3dbb024a0704ee3cc4e15c

Test-Parameters: trivial clientdistro=el7.8 clientarch=ppc64 testlist=sanityn
Signed-off-by: James Nunez <jnunez@whamcloud.com>
Change-Id: I39cc9d22e8a47eb8ef59ce8d30e1b6e9aa616a9a
Reviewed-on: https://review.whamcloud.com/40660
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>