Using default FnGetRefId behavior for LaunchConfig

FnGetRefId of LaunchConfig returns only physical_resource_name, but in
the case where a resource is not created, resource.id equals None. So the
result of FnGetRefId will be None too. It gives unpredictable behavior
during preview, when other resources return None too.

Change-Id: I425f777dbd0600e35354b0d5308cdaf701d85119
Closes-Bug: #1324493
Merge "Using default FnGetRefId behavior for LaunchConfig"