(scripts/review) Allow passing custom command to gerrit shell.
(scripts/review) Allow passing custom command to gerrit shell.

For example, build bot can be removed from all commits in chain as
follows:

  ./scripts/review --raw "gerrit set-reviewers \
                                 --remove 80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com"

Change-Id: Ib260d8549d7050b45c94f8e89ee5e43f338275fb
Reviewed-on: http://review.couchbase.org/89068
Tested-by: Aliaksey Artamonau <ce14b1c16e0fd654f926118eb8addbec5aff4ffa@couchbase.com>
Well-Formed: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Timofey Barmin <f30bdb2be8598fcffd705a378b25da4842d6bd7b@couchbase.com>

membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server