Set useBulkStmts to false for mariadb

This is a new config which works with mariadb 10.2.7+ but seems
to cause issues for that release with gerrit, lets disable it for now.

Bug: Issue 7074
Change-Id: I7062dc59a60eb5693cd44e7a03b33854dcc6a9d1

gerrit-server/src/main/java/com/google/gerrit/server/schema/MariaDb.java

@@ -40,6 +40,7 @@ class MariaDb extends BaseDataSourceType {
     b.append(port(dbs.optional("port")));
     b.append("/");
     b.append(dbs.required("database"));
+    b.append("?useBulkStmts=false");
     return b.toString();
   }