Defend against NULL _uas_tsx leading to Sprout crash
Merge pull request #642 from plfrancis/uas_tsx_crash

Defend against NULL _uas_tsx leading to Sprout crash
Use the new HttpStack 'controllers' API
Move chronos SAS logging utilities to httpstack_utils
Take latest cpp-common
Take latest cpp-common
Merge pull request #644 from Metaswitch/sto809

[Reviewer: Graeme][From: Alex] Sprout changes following HttpStack re-factor