repiar mongodb.launch

mongodb_store/mongodb_store.launch included the machine tag,
Maybe the launch file we had included intends to be used like http://wiki.ros.org/mongodb_store#Launching . 

It conflict with openni's rgbd_launch's machine (localhost ) tag and 
it make the error "Machine [localhost] already added and does not match duplicate entry".
So I copied most of the line from the mongodb_store.launch.