Fix floating ips when devtest.sh is hand executed

When devtest.sh is hand executed, the public interface of the
network node in overcloud is not added to br-ex bridge, which
makes floating ips unusable. This is caused by the fact that
we don't set the name of the public interface in devtest guide
(it's in devtest.sh, but it's not put to generated html doc).

Closes-Bug: #1252304

Change-Id: I9035b5ab26498954b46051f1b9bb982f0bc07c86

scripts/devtest_overcloud.sh

@@ -60,6 +60,11 @@ load-image -d $TRIPLEO_ROOT/overcloud-compute.qcow2
 
 OVERCLOUD_LIBVIRT_TYPE=${OVERCLOUD_LIBVIRT_TYPE:-";NovaComputeLibvirtType=qemu"}
 
+## #. Set the public interface of overcloud network node::
+##    ::
+
+NeutronPublicInterface=${NeutronPublicInterface:-'eth0'}
+
 ## #. Delete any previous overcloud::
 
 ##         heat stack-delete overcloud || true