netconf-connector-cfg information not correct

Reproduce:
1. Mount a Netconf device on Beryllium with the new netconf-node-topology introduced here: https://wiki.opendaylight.org/view/OpenDaylight_Controller:Config:Examples:Netconf#Spawning_netconf_connectors_via_topology_configuration
2. Do a GET on /restconf/operational/opendaylight-inventory:nodes/node/controller-config/yang-ext:mount/config:modules/
3. Search for keyword odl-sal-netconf-connector-cfg:username and odl-sal-netconf-connector-cfg:password
The odl-sal-netconf-connector-cfg:username is expected to be set as the device username provided in the mounting configuration: <username xmlns="urn:opendaylight:netconf-node-topology">vrouter-device-uname</username>, same as the odl-sal-netconf-connector-cfg:password
However, the odl-sal-netconf-connector-cfg:username and odl-sal-netconf-connector-cfg:password are always set to 'admin' instead