EX-4334 tests: disable sanity test_428 temporarily

EX-4334 tests: disable sanity test_428 temporarily

sanity test_428 is crashing regularly (about 1/15 runs) on b_es6_0.
Disable it until it is fixed.

Test-Parameters: trivial testlist=sanity env=ONLY=428,ONLY_REPEAT=180
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Id3c7722d5f4c4d084bf1dab83733aae8f9d8366f
Reviewed-on: https://review.whamcloud.com/46109
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>