[VOL-2404] : RW-Core changes for handling OLT Reboot Scenario

- When the OLT's connection status goes from REACHABLE to UNREACHABLE
  in ENABLED/DISABLED admin state, delete all the logical ports,
  child devices, logical device and device flows.

- When OLT's connection status becomes reachable again, child devices,
  ports will be re-discovered again. The logical device will be recreated
  again.

- Will not handle the case where OLT goes UNREACHABLE when OLT is disabled
  as part of voltha2.3 release

Change-Id: I34c0c538b44afa19e889e9631f0a738060a58fef
diff --git a/rw_core/core/common_test.go b/rw_core/core/common_test.go
index d07a095..8375f70 100644
--- a/rw_core/core/common_test.go
+++ b/rw_core/core/common_test.go
@@ -201,6 +201,14 @@
 				if done {
 					break
 				}
+			} else if d != nil && d.ParentId == "" { // case where logical device deleted
+				if verificationFunction(nil) {
+					ch <- 1
+					break
+				}
+				if done {
+					break
+				}
 			}
 			time.Sleep(retryInterval)
 		}