Flesh out call diversion tests
More Barriers for reliability
Boilerplate reduction
Add a pair of call waiting tests
Commenting and barriers
Merge pull request #80 from Metaswitch/call_waiting

[Reviewer: Mike] Add a pair of call waiting tests
More comments based on review feedback
Merge pull request #79 from Metaswitch/more_cdiv

[Reviewer: Mike] More CDiv tests