CamelKolabIMAPXConnManager: CamelKolabIMAPXStore init error propagation
CamelKolabIMAPXConnManager: CamelKolabIMAPXStore init error propagation

* propagate the error CamelKolabIMAPXStore initialization
  can throw now
* fixup for the parent class' get_connection()
  virtualization change

GNOME/evolution-kolab,GNOME/evolution-kolab