Revert "Harden against transiently unavailable backup transports"

This reverts commit 28b6d3829166935f50684c0152a154cd4f1bbb90.

Change-Id: Ic22ad1dae03f3f69cae632020dcdf2441846954a
Revert "Handle backup transport registration dynamically"

This reverts commit c46c4a6765196bcabf3ea89771a1f9067b22baad.

Change-Id: I098b0d79f8627ec5b37a762e4cfbf5e09534f16e