New test, extends test_subport_connectivity

Related-Bug: #1869244

Adding new test, test_subport_connectivity_soft_reboot
The test is checking trunks and ports are recreated during server
reboots, especialy in ovs_dpdk ports,
Since test flow is variant of test_subport_connectivity
Two methods added and used in the tests:
_create_servers_with_trunk_port
_check_servers_remote_connectivity

Change-Id: Ia5fbe680bb904680f52e0e15056d629717a643af
2 files changed