When the mininet is started before the openflowplugin feature is installed in the controller,
the openflowplugin starts, handshakes with the nodes and the nodes are successfully registered to MD-SAL.

But the FlowCapableInventoryProvider of the inventory manager application (in OpenflowPlugin) starts after the openflow handshake with the mininet is completed.
So the node updation notifications provided by the openflowplugin after the handshake completion are missed by the inventory manager application and the nodes are not added to the node datastore.
In these cases, the rest output for the operational node datastore is not populated.

This issue can be reproduced with the standard mininet linear topology itself.