ITS#7701 fix mdb_rebalance

Must copy tmp cursor back to real cursor when merging into tmp cursor.

libraries/liblmdb/mdb.c

@@ -7248,8 +7248,11 @@ mdb_rebalance(MDB_cursor *mc)
 	else {
 		if (mc->mc_ki[ptop] == 0)
 			rc = mdb_page_merge(&mn, mc);
-		else
+		else {
+			mn.mc_ki[mn.mc_top] += mc->mc_ki[mn.mc_top] + 1;
 			rc = mdb_page_merge(mc, &mn);
+			mdb_cursor_copy(&mn, mc);
+		}
 		mc->mc_flags &= ~(C_INITIALIZED|C_EOF);
 	}
 	return rc;