Use spinlocks instead of conn mutex to guard UPR notifications
similar to the way TAP does. This will decrease lock contention
since conn mutex is no longer needed here.

We now need to manipulate vbconns structure for UPR too:
add and remove connection for a stream based on vbid.

Also Refactored ConnMap/TapConnMap/UprConnMap as needed.

Change-Id: I86ac07d29f3575d334f3b7f27530dc6019adf294