rebaseline.py: look in gm-expected directory to see whether it's using git or svn

(before this change, it checked in the current working dir instead)

Review URL: https://codereview.chromium.org/18209010

git-svn-id: http://skia.googlecode.com/svn/trunk@9913 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed