srm: revert "refactor SchedulerFactory"

This reverts commit 1193536caf59037b34ca07b37a60203d458acd90 and
c547ddd5660884703044775d180ae22da01ba69a.

The intent of these patches was reasonable, but it broke being able to
start SRM with saved state.  Given the time available, this problem
cannot be fixed before the 2.8 release.