Use new tokio 1.x API functions.

Some functions have been renamed or removed as part of the tokio
1.x upgrade. This CL refactors the code to address that.

Also included are a couple minor rustfmt style changes as part of
submission.

Bug: 177808007
Test: mma
Change-Id: Ia147257b0cddb628866b34c9f755b1fe3c63e46d