lint: gerrit: fix misc cros lint errors
lint: gerrit: fix misc cros lint errors

BUG=chromium:327969
TEST=`cros lint lib/gerrit.py` doesn't complain
TEST=`./buildbot/run_tests` passes
TEST=`git grep IsChangeCommitted` doesn't show any callers using dry_run
TEST=`git grep SetReviewers` doesn't show any callers using project

Change-Id: If3766ad17978d1c64092056e5fcd667429dd92fe
Reviewed-on: https://chromium-review.googlesource.com/179792
Reviewed-by: Stefan Zager <542cb5b73770f9741bae40d34cf7a192bc7ad2cc@chromium.org>
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>

chadversary/chromiumos.chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite