[res] Make IdmapDaemon more robust

- Try to protect against the system shutdown when
  starting/stopping a service is impossible

- Fix the refcount for the service member in corner cases

- Don't access uninitialized connection object if its creation
  fails in the FRRO list function

- Get rid of the unneeded atomic int as it's always accessed
  under a lock

- Rename the start/stop service methods to explicitly point
  they're only called under a lock

Overall this makes the deadlocks much less probable, but not
gets rid of them completely

Fixes: 362083145
Fixes: 385464198
Test: build + boot
Flag: EXEMPT bugfix
Change-Id: Ib26f7317aec4dbb90616b630999e70ddcc5b884c