LU-11282 tests: log skip message for sanityn test_19

LU-11282 tests: log skip message for sanityn test_19

Log the skip message for sanityn test_19() rather than just echoing it
and returning success.  The current behaviour makes it difficult to
see if this test is being run or not.

Test-Parameters: trivial testlist=sanityn
Test-Parameters: testlist=sanityn mdtfilesystemtype=zfs ostfilesystemtype=zfs
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I05e2a9ef7c9fc5fb1be6533eab8bcb885f54ca6c
Reviewed-on: https://review.whamcloud.com/33214
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Elena Gryaznova <c17455@cray.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>