datapath-windows: Refactor core in Vport.c.

We do a bunch of changes that did not make sense to split up into
smaller patches:

1. Add descriptive comments to the important functions to clarify
   purpose.
2. s/OvsInitVportCommon/InitHvVportCommon - this function is common code
   for every port that shows up on the Hyper-V switch.
3. Introduce a InitOvsVportCommon() that is common code for evrey port
   that gets added from userspace. This is especially useful for ports
   that are not present on the Hyper-V switch. ie. tunnel ports and
   bridge-internal ports.
4. Fix OvsClearAllSwitchVports() to remove ports from both the lists:
   the ones added from Hyper-V as well as the ones added from OVS
   userspace.
5. Update OvsInitVxlanTunnel() to not call into InitHvVportCommon
   (formerly OvsInitVportCommon()) since it is not a port on the Hyper-v
   switch. In a later patch in the series, we'll call
   InitOvsVportCommon() for a VXLAN port.
6. 'numNonHvVports' increments and decrements ONLY for ports that are
   added from OVS userspace but not present on the Hyper-V switch.

Signed-off-by: Nithin Raju <nithin@vmware.com>
Acked-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Tested-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Acked-by: Ankur Sharma <ankursharma@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>