Reset inLoadChatlist only right before exit
in loadChatlistAsync().
Otherwise if loadChatlistAsync() is called
while the loop is running loadChatlist() or Util.sleep(100),
loadChatlistAsync() will see inLoadChatlist=false,
set needsAnotherLoad=true and start a second loop.
This way it is possible to spawn any number of background loops
running loadChatlist() simultaneously
so no debouncing actually happened.
Debouncing in SearchViewModel.updateQuery()
is fixed similarly by copying the code structure from loadChatlistAsync().
Previously it did not even have the lock.