Bug 2109. Fix VIM info DB update after vertical scaling, migrate and operate

Fix the path of the VDU record to update.
Fix unexpected keyword argument 'disk_over_commit' in live_migrate method because of Nova microversion change (Bug 2262)
Handle the OS-EXT-SRV-ATTR:host KeyError as this key is raised if the VIM account does not have admin credentials
Expand unit tests for vertical_scale, migrate and operate task creations

Change-Id: Ic7c1fe639fc0b8f917c46c6fe61fd4089a6970b4
Signed-off-by: Patricia Reinoso <patricia.reinoso@canonical.com>
diff --git a/RO-plugin/osm_ro_plugin/vimconn.py b/RO-plugin/osm_ro_plugin/vimconn.py
index b251d59..66fe190 100644
--- a/RO-plugin/osm_ro_plugin/vimconn.py
+++ b/RO-plugin/osm_ro_plugin/vimconn.py
@@ -123,12 +123,19 @@
 
 
 class VimConnNotImplemented(VimConnException):
-    """The method is not implemented by the connected"""
+    """The method is not implemented by the connector"""
 
     def __init__(self, message, http_code=HTTP_Not_Implemented):
         VimConnException.__init__(self, message, http_code)
 
 
+class VimConnInsufficientCredentials(VimConnException):
+    """The VIM account does not have efficient permissions to perform the requested operation."""
+
+    def __init__(self, message, http_code=HTTP_Unauthorized):
+        VimConnException.__init__(self, message, http_code)
+
+
 class VimConnector:
     """Abstract base class for all the VIM connector plugins
     These plugins must implement a VimConnector class derived from this