staging/lustre/ldlm: In ldlm_pools_fini make sure there was init first.

It turns out if you call ldlm_pools_fini without completing the
ldlm_pools_init, then attempt to unregister not yet registered
shrinkers makes the kernel very unhappy.
So make sure we have them registered first.
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/ldlm/ldlm_pool.c

@@ -1486,8 +1486,10 @@ EXPORT_SYMBOL(ldlm_pools_init);
 
 void ldlm_pools_fini(void)
 {
-	unregister_shrinker(&ldlm_pools_srv_shrinker);
-	unregister_shrinker(&ldlm_pools_cli_shrinker);
+	if (ldlm_pools_thread) {
+		unregister_shrinker(&ldlm_pools_srv_shrinker);
+		unregister_shrinker(&ldlm_pools_cli_shrinker);
+	}
 	ldlm_pools_thread_stop();
 }
 EXPORT_SYMBOL(ldlm_pools_fini);