Windows: Fix cm_serverRef ref counts

Windows: Fix cm_serverRef ref counts

Use Interlocked operations consistently

Simplify cm_ServerInsertList().  It no longer increments the
refCount on the serverRef object.  Instead it leaves the refCount
as is.  Its the caller's responsibility to add a reference if
required.

Add reference counts and hold locks in places where the
volume server list was used unprotected.

Change-Id: Ie65cdca4461e84c675e8a29e22cef3e15679fda7
Reviewed-on: http://gerrit.openafs.org/5248
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>