Ncp: Post the tasklet mUpdateChangedPropTask from constructor for initial reset flag. (#453)

src/ncp/ncp_base.cpp

@@ -388,6 +388,8 @@ NcpBase::NcpBase():
     otSetStateChangedCallback(&HandleNetifStateChanged, this);
     otSetReceiveIp6DatagramCallback(&HandleDatagramFromStack, this);
     otSetIcmpEchoEnabled(false);
+
+    mUpdateChangedPropsTask.Post();
 }
 
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