Revert "Harden against transiently unavailable backup transports"

This reverts commit 28b6d3829166935f50684c0152a154cd4f1bbb90.

Change-Id: I08fb95851d99a69de905cef0e191a7658f013bb3
Revert "Handle backup transport registration dynamically"

This reverts commit fe044f0952bb0d35653b877fb00f21e7e03de701.