engine: Do not fail on upgrade from 3.2 to 3.3

In case there are more than one VM or template configured
for port mirroring, the inner stored procedure used to
fail. The patch modifies the STP to support network with
several VMs or Templates using port mirroring.

Change-Id: I1b995dcde32ddf99b841bbddb19edf67d7061731
Bug-Url: https://bugzilla.redhat.com/1013341
Signed-off-by: Moti Asayag <masayag@redhat.com>