Revert "Temporarily excise B2BUA test"

This reverts commit ebcd467a555406c8d21f704b991d31039ac1aba4.
Reinstating B2BUA test
Merge branch 'master' into quaffify-b2bua
Fixes to B2BUA ISC test
Use Contact header from 200 OK in B2BUA script
Updating quaff submodule, cleaning up B2BUA script
Fix typo
Merge pull request #23 from Metaswitch/quaffify-b2bua

[No reviewer required] Add B2BUA test to live tests of ISC interface