tests/carp: make a 0.2 second pause before configuring second jail

for all scenarios where both jails have same priority/advskew. There is a
tiny chance that on both sides carp_master_down() will be executed in
parallel and advertisements will also fly through the bridge(4) in
parallel, thus both sides will switch to MASTER before receiving the
announcement from peer. This makes the test to fail. So far this
flakyness was observed for carp:vrrp_v4 only, but in theory it is possible
for any of the patched scenarios.

Note that this sleep does not prolong execution of the tests, as the first
jail is already configured, and if we slept before configuring the second,
we would sleep less in wait_for_carp().