Allow sync to terminate

[jsparber]

The SDK should stop syncing if the session is terminated from an other client. The termination makes the server returns 401 Unauthorized. Currently the sync response error is ignored and we try to sync again after a delay of 1s, see https://matrix-org.github.io/matrix-rust-sdk/src/matrix_sdk/client.rs.html#1692

[poljar]

This is somewhat related to #115.

[FlixCoder]

Is this stll the case? It looks like the sync now returns errors and it happened to me that it terminated with an error (that was not this though).

[gnunicorn]

yeah, this was effectively fixed with https://github.com/matrix-org/matrix-rust-sdk/pull/1037