Mark which tests depend on the MMTel TAS, and allow them to be disabled with NOMMTEL=true. These tests are often fragile due to race conditions, so this allows a subset of the live tests to be run confidently for continuous integration.
Add missing superclass call
Merge pull request #39 from Metaswitch/nommtel

[Reviewer: Mike] Mark which tests depend on the MMTel TAS, and allow them to be disabled ...