afs: Improve server refcount/active count tracing

afs: Improve server refcount/active count tracing

Improve server refcount/active count tracing to distinguish between simply
getting/putting a ref and using/unusing the server record (which changes
the activity count as well as the refcount).  This makes it a bit easier to
work out what's going on.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/20250224234154.2014840-10-dhowells@redhat.com/
Link: https://lore.kernel.org/r/20250310094206.801057-6-dhowells@redhat.com/