Autoroller: don't use GCE auth pathway

Even with the right credentials in place, git-cl will default to
using autogenerated GCE credentials when on a GCE machine. Tell
it to use the appropriate .gitcookies every time.

TBR=ehmaldonado@webrtc.org, kjellander@webrtc.org
NOTRY=True

Bug: chromium:765231
Change-Id: I761db91dde7db0c945e50e961c5687c835602dc4
Reviewed-on: https://webrtc-review.googlesource.com/1700
Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org>
Reviewed-by: Edward Lemur <ehmaldonado@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19879}
diff --git a/tools_webrtc/autoroller/roll_deps.py b/tools_webrtc/autoroller/roll_deps.py
index fa3c90b..26e2e09 100755
--- a/tools_webrtc/autoroller/roll_deps.py
+++ b/tools_webrtc/autoroller/roll_deps.py
@@ -409,7 +409,7 @@
     if not skip_cq:
       logging.info('Sending the CL to the CQ...')
       cmd.extend(['--use-commit-queue', '--send-mail'])
-    _RunCommand(cmd, extra_env={'EDITOR': 'true'})
+    _RunCommand(cmd, extra_env={'EDITOR': 'true', 'SKIP_GCE_AUTH_FOR_GIT': 1})
 
 
 def main():