make gm self-tests launch python unittests automatically
(not just within the rebaseline_server subdirectory)

Generally useful, but needed asap for my work on http://skbug.com/2752 ('split existing "gpu" GM results into "gl" and "gles"')

BUG=skia:677
NOTREECHECKS=True
NOTRY=True
R=rmistry@google.com
TBR=rmistry

Author: epoger@google.com

Review URL: https://codereview.chromium.org/398043002
5 files changed