OVS: Add an event on full-flow execution

[amorenoz]

Add full-flow execution event: Currently we get the action execution events but we don’t have an event that contains the entire flow, including the UFID:

Kernel support (i.e: tracepoint) might be needed in order to make the solution robust but we should try to have a kprobe-based solution for older kernels.

Should support both processed packets and OVS_PACKET_CMD_EXECUTE flows.