CBQE-513: Install script should flush firewall rules as one of its first steps

disable_firewall before wget command
wget uses tcp port

Change-Id: I6b1e00159a1820b34a810c44e27065093e465e0e
Reviewed-on: http://review.couchbase.org/23713
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Pavel Paulau <pavel.paulau@gmail.com>