Issue viewing flagged visits

[nehav39]

#237 Emergency button and queued visit issue
When health worker clicks on emergency button and uploads the patient details for the first time, the patient is visible on flagged visit on webui. But if the patient data is updated on visit summary screen, and is uploaded keeping the emergency button clicked, the patient is visible on queued visit section on webui

Solution: Change flagged from an encounter to a visit attribute. This will need changes to the android app