KolabMailSynchronizer: offline object deletion fix
KolabMailSynchronizer: offline object deletion fix

* in kolab_mail_synchronizer_transaction_prepare(), take into
  account that in PUSH operation, we can also have a deletion
* if we find we delete, then we return can_act=TRUE, telling
  that the deletion operation on the (old) object can happen
* in case of a server side change, we will not see the old
  IMAP UID has vanished, so we delete locally only

GNOME/evolution-kolab,GNOME/evolution-kolab