Add a "real" rule to the alert server

Return true if there is more than one issue with status "accepted".

Test locally by running:
$ alertserver -alsologtostderr -influxdb_database="graphite"
-influxdb_host="skiamonitor.com:10117" -influxdb_name="root"
-influxdb_password="<password from valentine>"
-use_metadata=false

BUG=skia:3036

Review URL: https://codereview.chromium.org/670703004