Most of the time in the BGP smoketest goes to config commits, at about 0.7 s each on a lab DUT. On top of that, test_bgp_99_bmp had a fixed 10 second sleep after killing bgpd so it would restart with the BMP module.

The sleep is now replaced by polling "show watchfrr". The test continues once bgpd has a new PID, watchfrr reports it as Up and Idle, and it has finished reading its configuration.

This is also more reliable than before: a fixed delay could pick up a PID that watchfrr then replaced. The timeout of 90 seconds follows the watchfrr restart timeout.