LU-10953 tests: disable sanity/300k on small setups

LU-10953 tests: disable sanity/300k on small setups

sanity/300k simulates creation of 512-stripes directory and
fails on small setup causing all subsequent tests to fail as
well.

Change-Id: I5e1d8d25ea364c0f49d9e114cc447cc40f951e2f
Signed-off-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-on: https://review.whamcloud.com/32148
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>