tests: Document ABI extension catchers

Our invalid-flags/params testcases are meant to catch abi extensions
by just testing for the next available flag/param. Unfortunately we
need that since without those we forgot to write testcases for these
new flags way too often :(

But it's not entirely clear why this is, so document this trick with
comments.

Also gem_wait wasn't this paranoid, so change the testcase to be so.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
3 files changed