Fix handling of stale CANCEL requests
Use find, not find_first_of
Pull in latest app-servers module
Merge pull request #730 from Metaswitch/sproutlet_cancel_race

[Reviewer Ellie] Fix handling of stale CANCEL requests
Merge pull request #731 from Metaswitch/icscf_uri

[Reviewer: Mike] Use find, not find_first_of