It is now possible to specify the amount of time
xdial server waits for rtremote status update resposes
with XDIAL_WAIT_FOR_RTREMOTE_STATE_RESPONSE_MS.
This can be used to make sure that up-to-date application
states are returned (instead of cached ones)

- if app instances are created outside of xdial, we might
  still be missing GDialApp instance.
- do not fetch app state asynchronously in case
  xdial is configured to wait for remote state responses
  anyway
- if current app state is 'stopped' or 'hidden'
  always return 201 on POST requests