Add thread locks on port routines for qos ext

Add thread locks on port routines for qos ext

Only one routine can be executed at one time. Handling port updates or
creations is a critical section of qos agent extension. With this patch
only one routine can be executed and in case of incoming update/create,
execution routine must wait until second routine is done with its job.

Change-Id: I28931d2be00dd87a8155a50afe008e03e9699f17
Partially-Implements: blueprint quantum-qos-api