Set sRemotePassiveRendezvousServer to NULL during shutdown

Since sRemotePassiveRendezvousServer is not reset, the weavestack
isnt shutdown cleanly. Set the var to NULL to shutdown the stack properly.

Bug: 47588
Test: Verified weavestack shutdown works cleanly.

Change-Id: Ib85c27225f3391b390ddae0caf0431c8dec4e6b1
diff --git a/src/lib/profiles/device-control/DeviceControl.cpp b/src/lib/profiles/device-control/DeviceControl.cpp
index cfa1938..9642f44 100644
--- a/src/lib/profiles/device-control/DeviceControl.cpp
+++ b/src/lib/profiles/device-control/DeviceControl.cpp
@@ -132,6 +132,8 @@
     mFailSafeArmed = false;
     mResetFlags = 0x0000;
 
+    sRemotePassiveRendezvousServer = NULL;
+
     // Kill any pending or completed Remote Passive Rendezvous.
     CloseRemotePassiveRendezvous();