Log console output for mac_learning and multicast tests

Would be useful to debug ssh failures in test vms.

Also for trunk_tests move check_connectivity method call to
_configure_vlan_subport as there SSH is attempted and that can
fail.

Related-Bug: #1952066
Change-Id: I64a1fd8118c9db1f337b7bf97bb9a77f974149b9
3 files changed