[autotest] Update gitignore to include creds/

creds will be deployed by puppet. Add it to gitignore.

TEST=None
BUG=chromium:567882

Change-Id: Iad893b5f0dbdddcf280c7ac869bb109d82da7b15
Reviewed-on: https://chromium-review.googlesource.com/318273
Commit-Ready: Fang Deng <fdeng@chromium.org>
Tested-by: Fang Deng <fdeng@chromium.org>
Reviewed-by: Dan Shi <dshi@google.com>
diff --git a/.gitignore b/.gitignore
index 41a77ec..8d7bf84 100644
--- a/.gitignore
+++ b/.gitignore
@@ -53,6 +53,7 @@
 # These exist on the production servers.
 bug_filing_oauth_credentials.dat
 gmail_api_credentials.dat
+creds/
 site_utils/autotest_private/
 site_utils/autotest_tools/
 site_utils/devserver/