tests: Make verify_rib wait up to 40 seconds.

tests: Make verify_rib wait up to 40 seconds.

Under heavy load I am seeing verify_rib failing after 12 seconds
but succeeding after 17:

2022-05-19 18:52:54,374 DEBUG: topolog: Exiting lib API: verify_rib
2022-05-19 18:52:54,374 DEBUG: topolog: Function returned True
2022-05-19 18:52:54,374 WARNING: topolog: RETRY DIAGNOSTIC: SUCCEED after FAILED with requested timeout of 12.0s; however, succeeded in 14.7s, investigate timeout timing

There is no reason to not have the test wait a bit longer for very very
heavily loaded systems.  Change the time to 40 seconds.

Signed-off-by: Donald Sharp <sharpd@nvidia.com>