tests: Run OVS_WAIT_WHILE, OVS_WAIT_UNTIL in main shell environment.

tests: Run OVS_WAIT_WHILE, OVS_WAIT_UNTIL in main shell environment.

AT_CHECK runs its commands in a subshell.  That means that (among other
effects), any variable assignments within its commands will disappear after
the commands' completion.  That doesn't matter for any of the existing
users, which don't do the sorts of things that affect an outer shell
environment anyhow, but an upcoming user wants to make a shell assignment
that persists.  This commit makes that possible, by using AT_CHECK
(actually AT_FAIL_IF but it's moot) only upon failure instead of bracketing
the entire test.

Signed-off-by: Ben Pfaff <blp@ovn.org>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Acked-by: Flavio Leitner <fbl@sysclose.org>