make sure new_zone_lock is locked before unlocking it

it was possible for the count_newzones() function to try to
unlock view->new_zone_lock on return before locking it, which
caused a crash on shutdown.

bin/named/server.c

@@ -7574,6 +7574,8 @@ count_newzones(dns_view_t *view, ns_cfgctx_t *nzcfg, int *num_zonesp) {
 
 	REQUIRE(num_zonesp != NULL);
 
+	LOCK(&view->new_zone_lock);
+
 	CHECK(migrate_nzf(view));
 
 	isc_log_write(named_g_lctx, NAMED_LOGCATEGORY_GENERAL,
@@ -7582,8 +7584,6 @@ count_newzones(dns_view_t *view, ns_cfgctx_t *nzcfg, int *num_zonesp) {
 		      "for view '%s'",
 		      view->new_zone_db, view->name);
 
-	LOCK(&view->new_zone_lock);
-
 	CHECK(nzd_count(view, &n));
 
 	*num_zonesp = n;
@@ -12911,6 +12911,10 @@ cleanup:
 	return (result);
 }
 
+/*
+ * Migrate zone configuration from an NZF file to an NZD database.
+ * Caller must hold view->new_zone_lock.
+ */
 static isc_result_t
 migrate_nzf(dns_view_t *view) {
 	isc_result_t result;
@@ -12926,8 +12930,6 @@ migrate_nzf(dns_view_t *view) {
 	MDB_val key, data;
 	ns_dzarg_t dzarg;
 
-	LOCK(&view->new_zone_lock);
-
 	/*
 	 * If NZF file doesn't exist, or NZD DB exists and already
 	 * has data, return without attempting migration.
@@ -13063,8 +13065,6 @@ cleanup:
 		result = nzd_close(&txn, commit);
 	}
 
-	UNLOCK(&view->new_zone_lock);
-
 	if (text != NULL) {
 		isc_buffer_free(&text);
 	}