Dispatch MatrixActions synchronously
Dispatch MatrixActions synchronously

Otherwise we risk blocking the dispatches on other work, and they
do not need to be done asynchronously.

This emerged as a bug where the room list appeared empty until
MatrixActions.sync dispatches all occured in one big lump, well
after the sync events being emitted by the js-sdk.

aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,aperezdc/matrix-react-sdk