[paging] Unbreak breakge when moving things into paging.c

By calling _paging_request_stop with NULL for the lchan we
have never used the paging complete callback... I didn't
spot that when moving the code over and thought it is a great
simplification to not call paging_request_stop first and then
loop... *sigh*

restore the old behaviour. Call the callback first and then
free the requests.
diff --git a/openbsc/src/paging.c b/openbsc/src/paging.c
index e647b33..df11da0 100644
--- a/openbsc/src/paging.c
+++ b/openbsc/src/paging.c
@@ -278,6 +278,8 @@
 {
 	struct gsm_bts *bts = NULL;
 
+	_paging_request_stop(_bts, subscr, lchan);
+
 	do {
 		/*
 		 * FIXME: Don't use the lac of the subscriber...
@@ -290,7 +292,8 @@
 			break;
 
 		/* Stop paging */
-		_paging_request_stop(bts, subscr, NULL);
+                if (bts != _bts)
+			_paging_request_stop(bts, subscr, NULL);
 	} while (1);
 }