Use strict match for mod-flow

From the ovs doc, if mod-flow is used without --strict, priority is not
used in matching.
This will cause problem for downstream set_drop when
duplicate_nic_upstream is disabled.

For example:

When set_drop is applied to upstream_nic_flow(sonic-net#1), mod-flow will match both
flow sonic-net#2 and flow  sonic-net#3 as priority is not used in flow match.

So let's enforce strict match for mod-flow.

Signed-off-by: Longxiang Lyu <lolv@microsoft.com>

ansible/dualtor/nic_simulator/nic_simulator.py

@@ -97,7 +97,7 @@ class OVSCommand(object):
     OVS_VSCTL_LIST_PORTS_CMD = "ovs-vsctl list-ports {bridge_name}"
     OVS_OFCTL_DEL_FLOWS_CMD = "ovs-ofctl del-flows {bridge_name}"
     OVS_OFCTL_ADD_FLOWS_CMD = "ovs-ofctl add-flow {bridge_name} {flow}"
-    OVS_OFCTL_MOD_FLOWS_CMD = "ovs-ofctl mod-flows {bridge_name} {flow}"
+    OVS_OFCTL_MOD_FLOWS_CMD = "ovs-ofctl --strict mod-flows {bridge_name} {flow}"
     OVS_OFCTL_DEL_GROUPS_CMD = "ovs-ofctl -O OpenFlow13 del-groups {bridge_name}"
     OVS_OFCTL_ADD_GROUP_CMD = "ovs-ofctl -O OpenFlow13 add-group {bridge_name} {group}"
     OVS_OFCTL_MOD_GROUP_CMD = "ovs-ofctl -O OpenFlow13 mod-group {bridge_name} {group}"