This typo was introduced in https://codereview.chromium.org/106403003.

Rename options.dryrun to options.dry_run.

R=agable@chromium.org,dpranke@chromium.org
BUG=none
TEST=none

Review URL: https://codereview.chromium.org/138623008

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@250802 0039d316-1c4b-4281-b951-d872f2087c98