Add validation to ping the default gateway(s)
Add validation to ping the default gateway(s)

This patch adds a new function that runs on all nodes so that
all default gateways are ping tested early on during the
installation process (before any puppet is executed)

Note: this change depends on the static control plane network IPs
because some distros allow/create multiple default routes without
this patch (see depends-on below).

Depends-On: Ib267e6dcf2d5ff77f7a82ee20a123965c2d07565

Change-Id: Ida125e79f3e549cae66be9dbd562197afa6400a5

openstack/tripleo-heat-templates,trozet/opnfv-tht,dprince/tripleo-heat-templates,openstack/tripleo-heat-templates,bcrochet/tripleo-heat-templates,trozet/tripleo-heat-templates,trozet/opnfv-tht,dprince/tripleo-heat-templates,bcrochet/tripleo-heat-templates,trozet/tripleo-heat-templates,bcrochet/tripleo-heat-templates,trozet/opnfv-tht