tests: Allow convergence before adding multicast routes

tests: Allow convergence before adding multicast routes

Current code adds a new vlan interface, sets up ospf and
pim on it and immediately starts shoving data down the pipes.
This of course has the fun thing where the IGP and pim do not
always come up in a nice neat manner and the test is looking
for state from a nice neat come up, even though pim is `working`
correctly it is not correct for what the test wants.

Modify the code to ensure that ospf is up and has propagated
the route where it is needed as well as that pim neighbors have
properly come up, then initiate the multicast streams and igmp
reports.

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