VOL-2970 - Improved readability & traceability of startup code.

Changed Start() function to implement majority of the startup functionality, with less helpers.  Start() also defines local variables for each component created, to avoid accidentally using a component that isn't ready.
Also merged the rwCore into the Core.
Also changed Core to cancel a local context to on shutdown, and then wait for shutdown to complete.

Change-Id: I285e8486773476531e20ec352ff85a1b145432bf
diff --git a/rw_core/core/device/manager.go b/rw_core/core/device/manager.go
index b0128a5..9990104 100755
--- a/rw_core/core/device/manager.go
+++ b/rw_core/core/device/manager.go
@@ -32,7 +32,6 @@
 	"github.com/opencord/voltha-go/rw_core/utils"
 	"github.com/opencord/voltha-lib-go/v3/pkg/kafka"
 	"github.com/opencord/voltha-lib-go/v3/pkg/log"
-	"github.com/opencord/voltha-lib-go/v3/pkg/probe"
 	"github.com/opencord/voltha-protos/v3/go/common"
 	ic "github.com/opencord/voltha-protos/v3/go/inter_container"
 	ofp "github.com/opencord/voltha-protos/v3/go/openflow_13"
@@ -53,7 +52,6 @@
 	stateTransitions        *TransitionMap
 	clusterDataProxy        *model.Proxy
 	coreInstanceID          string
-	exitChannel             chan int
 	defaultTimeout          time.Duration
 	devicesLoadingLock      sync.RWMutex
 	deviceLoadingInProgress map[string][]chan int
@@ -61,7 +59,6 @@
 
 func NewManagers(proxy *model.Proxy, adapterMgr *adapter.Manager, kmp kafka.InterContainerProxy, endpointMgr kafka.EndpointManager, corePairTopic, coreInstanceID string, defaultCoreTimeout time.Duration) (*Manager, *LogicalManager) {
 	deviceMgr := &Manager{
-		exitChannel:             make(chan int, 1),
 		rootDevices:             make(map[string]bool),
 		kafkaICProxy:            kmp,
 		adapterProxy:            remote.NewAdapterProxy(kmp, corePairTopic, endpointMgr),
@@ -71,9 +68,10 @@
 		defaultTimeout:          defaultCoreTimeout * time.Millisecond,
 		deviceLoadingInProgress: make(map[string][]chan int),
 	}
+	deviceMgr.stateTransitions = NewTransitionMap(deviceMgr)
+
 	logicalDeviceMgr := &LogicalManager{
 		Manager:                        event.NewManager(),
-		exitChannel:                    make(chan int, 1),
 		deviceMgr:                      deviceMgr,
 		kafkaICProxy:                   kmp,
 		clusterDataProxy:               proxy,
@@ -87,20 +85,6 @@
 	return deviceMgr, logicalDeviceMgr
 }
 
-func (dMgr *Manager) Start(ctx context.Context) {
-	logger.Info("starting-device-manager")
-	dMgr.stateTransitions = NewTransitionMap(dMgr)
-	probe.UpdateStatusFromContext(ctx, "device-manager", probe.ServiceStatusRunning)
-	logger.Info("device-manager-started")
-}
-
-func (dMgr *Manager) Stop(ctx context.Context) {
-	logger.Info("stopping-device-manager")
-	dMgr.exitChannel <- 1
-	probe.UpdateStatusFromContext(ctx, "device-manager", probe.ServiceStatusStopped)
-	logger.Info("device-manager-stopped")
-}
-
 func (dMgr *Manager) addDeviceAgentToMap(agent *Agent) {
 	if _, exist := dMgr.deviceAgents.Load(agent.deviceID); !exist {
 		dMgr.deviceAgents.Store(agent.deviceID, agent)