Use grep -e --force instead of grep "--force" since apparently the latter doesn't work properly in all cases.

BUG=441072
TEST=No errors from gclient :/

Review URL: https://codereview.chromium.org/802513003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@293380 0039d316-1c4b-4281-b951-d872f2087c98