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
Use separate stack-create overcloud call in docs

Currently, devtest_overcloud doc contains stack-create overcloud
call, which accepts parameters, that we don't expose to users in
devtest story (e.g. NeutronPublicInterfaceDefaultRoute). It would
be less confusing to users, if we passed only parameters, that
are defined in devtest doc and rely on defaults of the overcloud
template for the rest of parameters.

Change-Id: Iec097bee09ff06997fcfd7a4ec4a3d639ad6c77f
Merge "Fix floating ips when devtest.sh is hand executed"
Merge "Use separate stack-create overcloud call in docs"