Tidy status handling in rendservice.c

We had some code to fix up the 'status' return value to -1 on error
if it wasn't set, but it was unreachable because our code was
correct.  Tweak this by initializing status to -1, and then only
setting it to 0 on success.  Also add a goto which was missing: its
absence was harmless.

[CID 718614, 718616]