Fix issue with receiving loop getting stuck

[gferon]

#363 attempted to make things better but actually ended up making it worse.

The polling logic I introduced in #343 using was wrong in all cases.

The real issue was two-fold:

• The identified websocket was being initialised (or reused) for the AccountManager instance we prepare, and then re-initialised by the message receiving loop, which requires a fresh websocket to make sure we start the sync from the start (and then receiving EmptyQueue). I should investigate why this doesn't blow in your face with a nice error message - it hangs instead. Re-ordering and reusing variables correctly
• The way we were polling on the refresh registration task was absolutely not correct, because it would essentially be dropped once we receive the first element of the decrypted messages stream.