New instances can now join Networks created in previous deployments

Names of the Network and Subnet Heat resources were placed in the Runtime fields of NewNetwork class,
so they were lost between the redeploymnet.
Now they are re-generated before each use based on the persisted information (names and ids)

Change-Id: I4dcb9915fac04590105b6ec284b4b0274c722b3f
Partial-Bug: #1324094
Merge "New instances can now join Networks created in previous deployments"