Merge pull request #17296 from php-coder/refactor_test_admit

Automatic merge from submit-queue (batch tested with PRs 17369, 17296).

admission_test.go(TestAdmit): compare SecurityContexts instead of particular members

This makes the test close to the upstream implementation.

Extracted from #16934 (comment)

PTAL @liggitt @pweil- @adelton @simo5

Author: openshift-merge-robot