VOL-1548 Fixed errors in openolt adapter when executing a delete command.

Change-Id: Ib629052d6c37495e6d168f45e25c9111aac88ebe
diff --git a/python/adapters/openolt/openolt.py b/python/adapters/openolt/openolt.py
index 682b62c..9c5f799 100644
--- a/python/adapters/openolt/openolt.py
+++ b/python/adapters/openolt/openolt.py
@@ -212,7 +212,8 @@
         handler = self.devices[device.id]
         handler.delete()
         del self.devices[device.id]
-        del self.logical_device_id_to_root_device_id[device.parent_id]
+        if device.parent_id in self.logical_device_id_to_root_device_id.keys():
+            del self.logical_device_id_to_root_device_id[device.parent_id]
         return device
 
     def get_device_details(self, device):