Allow skipping 'master.' prefix in master restart tool.
Allow skipping 'master.' prefix in master restart tool.

So that this works:
    cit restart tryserver.infra

R=hinoka@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1285193002

nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra