The dhcp agent calls ovs_vsctl so it will fail if using rootwrap
and these aren't specified. The reason why this was working using
rootwrap before is because there are other filters in
etc/quantum/rootwrap.d that specifiy ovs_vsctl which
allows the agent to make those calls. Fixes bug 1090072
Change-Id: I509c191c97e7187361a09788e841ebb5a9f934c7
aad4a48d4b