[IoTConnectivity] Handle the exception for getting Dictionary item (#1092)

[IoTConnectivity] Handle the exception for getting Dictionary item (#1092)

We should prevent the crash in next exception case.

Unhandled exception.

System.Collections.Generic.KeyNotFoundException: The given key '2' was not present in the dictionary.
 at System.Collections.Concurrent.ConcurrentDictionary`2.ThrowKeyNotFoundException(Object key)
 at System.Collections.Concurrent.ConcurrentDictionary`2.get_Item(TKey key)
 at Tizen.Network.IoTConnectivity.RemoteResource.NativePutResultCallbackHandler(IntPtr resource, Int32 err, Int32 requestType, IntPtr responseHandle, IntPtr userData)