CBQE-2095:  View warmup tests fail with error , unable to connect to
node
Temporary fix to _execute_boot function to flush firewall rules.
Ideally this should be in sync with the basetests.py function of
_kill_nodes()

Change-Id: I8c9e77d277fd78fce8c6ab2790553be611961994
Reviewed-on: http://review.couchbase.org/34194
Reviewed-by: Ketaki Gangal <ketakigangal@gmail.com>
Tested-by: Ketaki Gangal <ketakigangal@gmail.com>