tests: all_protocol_startup needs some tweaks to allow for processing

tests: all_protocol_startup needs some tweaks to allow for processing

The nexthop group code is installing routes and nexthop groups
and immediately expecting zebra to have processed the results
as a result there is a situation when the CI system is under
intense load that the nexthop group might not have been processed.

Add a bit of code to allow the test to give FRR some time
to finish work before declaring it not working.

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