[Fullstack] Change time waiting for async ping results
[Fullstack] Change time waiting for async ping results

During agents restart there is async ping run and there is
called function to wait until all async ping workers will
finish their job.

In TestHAL3Agent.test_ha_router_restart_agents_no_packet_lost
there are 60 pings sent with 1 second timeout so default
wait_until_true timeout which is set to 60 seconds might not
be enough in some cases.
Because of that wait_until_true timeout is now set as
twice higher value than is needed to number of packets to send
with ping_timeout.

This should give enough time to finish all workers.

Change-Id: Ia7c3755c2ba5029bdab3c1dd30b305f3bde19740
Closes-Bug: #1775183

openstack/neutron,openstack/neutron,noironetworks/neutron,mahak/neutron,mahak/neutron,mahak/neutron,huntxu/neutron,noironetworks/neutron,openstack/neutron,huntxu/neutron