PR19601: testcase improvement

The test can now catch all cases:
 - no removal of the 'no-integrated-as' flag
 - bogus removal of the flag, like when the remove_if was not followed by an erase

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@207787 91177308-0d34-0410-b5e6-96231b3b80d8