Resolve "Subscribe to network element on creation in controller"

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Related to #324

controller/api/initialise_test.go

@@ -206,6 +206,8 @@ func bootstrapUnitTest() {
 		conflict.Metadata{ResourceVersion: 0})
 	_ = networkElementService.Add(mne)
 
+	networkElementWatcher := nucleus.NewNetworkElementWatcher(networkElementService, eventService)
+
 	pndService := &mocks.PndService{}
 	pndService.On("GetAll").Return([]networkdomain.NetworkDomain{}, nil)
 	pndService.On("Add", mock.Anything).Return(nil)
@@ -234,6 +236,7 @@ func bootstrapUnitTest() {
 		rpb.NewPluginRegistryServiceClient(&grpc.ClientConn{}),
 		csbi.NewCsbiServiceClient(&grpc.ClientConn{}),
 		func(u uuid.UUID, c chan networkelement.Details) {},
+		networkElementWatcher,
 	)
 
 	ppb.RegisterPndServiceServer(s, northbound.Pnd)