Avoid use of fail here

It causes a reraise with a bunch of extra entries that we don't need.

api-daemon/pvcapid/vmbuilder.py

@@ -100,7 +100,7 @@ class VMBuilder(object):
         log_err(None, msg)
 
     def fail(self, msg, exception=ProvisioningError):
-        fail(None, msg, exception=exception)
+        raise exception(msg)
 
     #
     # Primary class functions; implemented by the individual scripts