datapath-windows: Removed memory barrier and master lock

datapath-windows: Removed memory barrier and master lock

There is no need to enforce Netlink serialization on transactions
sent from userspace. The access to the driver's shared resources
is synchronized anyway. Thus I have removed the master lock.

I also removed the memory barrier from filter dispatch routine. A
memory barrier is already in place in OvsReleaseSwitchContext
function, due to the use of InterlockedCompareExchange function.

Signed-off-by: Sorin Vinturis <svinturis@cloudbasesolutions.com>
Acked-by: Eitan Eliahu <eliahue@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>