gclient_scm_test is really flaky and is a pain to maintain. gclient_scm.py
coverage is good enough with gclient_smokte_test.

TBR=chase

Review URL: http://codereview.chromium.org/3155024

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@56351 0039d316-1c4b-4281-b951-d872f2087c98