[UHN-MA-71] Availability switch not updated

Issue: When the user loads the app but is already logged in, availability status is not fetched from the db. 
Result: The toggle switch is inconsistent with the db and the status that other users see. When logging out, availability status may not be updated when it should be (DrawerContent.js:25)
Expect: Availability should be fetched every time the app is launched.