Fix default template for AWS::CloudWatch::Alarm with Ceilometer

Existing template assumes certain parameters to be delimited
strings rather than lists and uses 'Fn::Split' to convert them
to list. However, delimitedstring representations of parameters
are by default converted to list for CommaDelimitedList types.
Also includes change for CommaDelimitedList to accept empty string.

Change-Id: Ib566f1d098c575a80c4f1a975eaaaac93d70af34
Closes-Bug: #1316842
Merge "Fix default template for AWS::CloudWatch::Alarm with Ceilometer"