Task seems to capture trigger.PatientID

https://trello.com/c/BEBgBGPR/877-bug-task-doesn-t-seem-to-capture-trigger-patientid

Replace patientId to the id generated by CouchDB, change findBy method in patientUpdate,
fixed order in task-channel and check if new motechId already exists

Change-Id: Idb35d37517bd99d377fba874fbaa97c565cfc9fb