ApiHelper: use XMLRPCFactory.instantiate instead of instantiating XMLRPCClient directly
StatsActivity: use XMLRPCFactory.instantiate instead of instantiating XMLRPCClient directly
Merge pull request #1415 from wordpress-mobile/issue/1413-use-xmlrpcfactory

fix #1413 use XMLRPCFactory.instantiate instead of instantiating XMLRPCClient directly