This allows "git cl try" to just work for projects without any PRESUBMIT
but with cq.cfg in default location (infra/config/cq.cfg). This also
ships all presubmit bots, since these usually fail LGTM checks anyway.

BUG=522909

Review URL: https://codereview.chromium.org/1579423004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@298251 0039d316-1c4b-4281-b951-d872f2087c98