Limit the number of preloader sessions to one.

The current behaviour is that a request with another session
ID is made when a session is active, the request is denied.
This prevents trashing if multiple apps were to request preloads
with different IDs. This also means the first one wins always.

bug: 5066968

Change-Id: I7454b929255c3f845abd4463dbe07bb2d5afcf5f
1 file changed