If a user has no groups, no group sync message is sent. This is a normal
result that should result in a success event rather than a timeout.
// FREEBIE
Similar in function to an xhr request, a textsecure.SyncRequest object
is initialized from a message sender and receiver pair and initiates a
request for sync from the master device. It later fires a success event
when both contacts and groups are done syncing, or a timeout event after
one minute.
// FREEBIE
