update comment filter for gerrit 2.8

In Gerrit 2.4.x stream event, comments contained just the comment.  Gerrit 2.8 appends
the patch id to the comment string.  This change updates the regex to match on both 2.4
and 2.8 stream events.

gerrit 2.4.x - "comment":"recheck no bug"
gerrit 2.8.x - "comment":"Patch Set 4:\n\nrecheck no bug"

Change-Id: I94799fc56719fb98cb04c44cda7e39a65722c088
Merge "update comment filter for gerrit 2.8"