Controller config ReST call now reports non-existent mount point.

This URL is being used in system tests to determine that all necessary modules are up.

http://localhost:8181/restconf/config/opendaylight-inventory:nodes/node/controller-config/yang-ext:mount/config:module

The tests are now failing because this is being returned:

{
"errors": {
"error": [

{ "error-type": "protocol", "error-tag": "data-missing", "error-message": "Mount point does not exist." }

]
}
}

The failure occurs on the master branch with controllers in single node and clustered configurations. The failure does not occur on the Lithium branch.