Fix update.py to not replace oslo-incubator

update.py was replacing olso-incubator with <project>-incubator,
when oslo-incubator should have been left as-is, since there's no
keystone-incubator for example.

Change-Id: I9717f905c511d03ac9746537898afe161b3a179a
Merge "Fix update.py to not replace oslo-incubator"