paunch apply should exit nonzero for failures

Exit with the return code (nonzero) in case of a failure during paunch
apply. When executing commands such as "docker run..." the actual docker
return code will be used as the exit code, which is what we want so that
the ansible tasks running paunch will actually fail.

Change-Id: Ic656d27c4428249c5394dcd9f998c5bb4e264250
Partial-Bug: #1707997

paunch/cmd.py

@@ -68,13 +68,15 @@ class Apply(command.Command):
         with open(parsed_args.file, 'r') as f:
             config = yaml.safe_load(f)
 
-        paunch.apply(
+        stdout, stderr, rc = paunch.apply(
             parsed_args.config_id,
             config,
             managed_by='paunch',
             labels=labels
         )
 
+        return rc
+
 
 class Cleanup(command.Command):