Allow boot2docker-cli ssh [commands] to pass through to ssh

This will let users and scripts to get state information from inside the vm

like getting the host only IP address:

     $ boot2docker-cli -m 123 ssh ip addr show eth1 |sed -ne 's/^[
     \t]*inet[ \t]*\([0-9.]\+\)\/.*$/\1/p'
     192.168.59.103