[client] lgmp: skip release after session loss

Heartbeat expiry does not change the LGMP session ID. Queue operations
can therefore accept ownership releases into stale shared memory after
a guest reboot, where no host remains to advance the acknowledgement
serial.

Skip graceful clipboard and input ownership release when the session is
already invalid. Keep the existing timeout and warning for a live host
that fails to process the release.

client/transports/LGMP/input.c

@@ -907,7 +907,8 @@ static void logStats(const struct LGMPInputCounters * stats)
 static void releaseOnDisconnect(LGMPInput * input)
 {
   if (!input->queue || !input->stream || !input->publishedClaimed ||
-      !input->publishedGeneration)
+      !input->publishedGeneration ||
+      !lgmpClientSessionValid(input->client))
     return;
 
   KVMFRInputMessage message =