Occasionally fail to retrieve mail at startup: Closes #5381
Occasionally fail to retrieve mail at startup: Closes #5381

A timing window opened in the recent changes to Deserializer that
allowed for a ServerData "received" signal to be fired before the
ClientConnection.connect_async() call completed.  This is to be
expected in a heavily asynchronous library.  The ClientConnection
"connect" signal, however, is guaranteed to be fired before the
"received" signal, so that is used to synchronize some state in
ClientSession needed for login.

abn/geary,mjog/geary,robol/geary,geekvigilante/geary,kyoushuu/geary,orlandosanchez/geary,tshikaboom/geary,mjog/geary,jimbonator/geary,martinra/geary,rschroll/geary,glebihan/geary,emersion/geary,mpdeimos/geary,AtticHacker/geary,martinra/geary,githubnemo/geary,didrocks/geary,robol/geary,tshikaboom/geary,emersion/geary,kyoushuu/geary,AtticHacker/geary,aatishnn/geary,rschroll/geary,dominickm/Geary,glebihan/geary,jimbonator/geary,robol/geary,MohamedIM/geary-unofficial,aatishnn/geary,jimbonator/geary,glebihan/geary,githubnemo/geary,kpiwko/geary,AtticHacker/geary,orlandosanchez/geary,martinra/geary,dominickm/Geary,emersion/geary,githubnemo/geary,tshikaboom/geary,aatishnn/geary,mjog/geary,orlandosanchez/geary