ALSA backend: separate flags for is-running and should-be-running
Revert "ALSA backend: separate flags for is-running and should-be-running"

Theoretically one could alter the plugins after a delivery even on a
frozen track. ..or even change settings, the ordering and add/remove
plugins after the frozen part of a track.

We won't go there. Frozen is frozen. this API is not needed after all.

This reverts commit 6d89488d64d44ed4b3283308a583b320300553c8.