Catch a NotFound exception in signal_responder delete

If the alarm does not get created (error condition) and
the url does not get created (no one referenced it) then
the delete will fail with a NotFound.

Change-Id: I431ebef9b9341548176d977e336558df9f5deb6c
Rename OS::Metering::Alarm to OS::Ceilometer::Alarm

The other resources are named by project so this is to
try and be more consistent.

There is a mapping to allow the original name to work.

Change-Id: If60cc577a5a770bdaada70c7eae1ae3fc1776056
Merge "Catch a NotFound exception in signal_responder delete"
Merge "Rename OS::Metering::Alarm to OS::Ceilometer::Alarm"