In case proxy host on the environment for some reason
does not have routing to the external network
spawn a VM on external network to use it as a proxy
host for sending traffic to the VM under test.
Note: on podified environment we can not ping VM in
DVR test from a local ip since tempest is running on
one of the OCP cluster nodes and FIP-related traffic
will be captured on the gateway node (when only
compute nodes are expected) and thus affecting the
results.
Change-Id: I35def1d0d0e419cbcf552bc6148ed112567aa8f6
f89d5d40d2