Toggle instance state API may not work when there are realtime segments in OFFLINE state

Handle the case when realtime segments are in OFFLINE state because there're some problem with realtime segment consumption, and realtime segment will mark itself as OFFLINE in ideal state.

The current API of toggling instance state just checks whether the current state is the same as `OFFLINE` state, while there's one exception that realtime segment will intentionally mark itself as `OFFLINE` in ideal state when there's some problem during the consumption.

No files or tests are named. Start by tracing the current instance-state toggle API and how realtime segments mark themselves OFFLINE during consumption problems. Done means the API distinguishes that intentional realtime-segment state from an instance that should be toggled offline.

Written by the indexing model from the issue text.