Setting root passwd no longer fails silently.

Fixes LP 1022961

Previously an attempt to set the root password would fail silently if
for example the driver did not support this action.

To avoid the user being misled that the password change had succeeded,
we now report any failure by changing the MEP for set_admin_password
RPC from cast to call.

Change-Id: I1fd7b925e9226d30892f3a7cc4ddb938ff678a55

nova/exception.py

@@ -1085,6 +1085,12 @@ class InstanceTypeCreateFailed(NovaException):
     message = _("Unable to create instance type")
 
 
+class InstancePasswordSetFailed(NovaException):
+    message = _("Failed to set admin password on %(instance)s "
+                "because %(reason)s")
+    safe = True
+
+
 class SolidFireAPIException(NovaException):
     message = _("Bad response from SolidFire API")