Add support for "signals" to os-refresh-config

The new software config / deployments resources use signals.

A subtle difference between wait condition handles and signals in Heat
is that signals use POST, but wait conditions use PUT. This has
historical reasons that mostly are due to Amazon compatibility. We need
to continue to support both until we can eliminate all use of wait
conditions.

Change-Id: I69d9103b07100f700fb71a2cbbf267042625e7a7
Merge "Add support for "signals" to os-refresh-config"