Fix for HPE MSA 2050 login failures

When authenticating to the array, use the 'response-type-numeric'
value to determine success, rather than doing a string match against the
'response-type' string, which is not guaranteed to be consistent.

Change-Id: I47fe1ff2dd5e24fffd5118aeab9473774eb58a61
Closes-Bug: #1808968

cinder/volume/drivers/dothill/dothill_client.py

@@ -56,10 +56,12 @@ class DotHillClient(object):
         self._session_key = None
         try:
             tree = etree.XML(xml)
-            if (tree.findtext(".//PROPERTY[@name='response-type']") ==
-                    "success"):
-                self._session_key = (
-                    tree.findtext(".//PROPERTY[@name='response']"))
+            # The 'return-code' property is not valid in this context, so we
+            # we check value of 'response-type-numeric' (0 => Success)
+            rtn = tree.findtext(".//PROPERTY[@name='response-type-numeric']")
+            session_key = tree.findtext(".//PROPERTY[@name='response']")
+            if rtn == '0':
+                self._session_key = session_key
         except Exception as e:
             msg = _("Cannot parse session key: %s") % e.msg
             raise exception.DotHillConnectionError(message=msg)