Drop connection if it might be bad on APPEND
Drop connection if it might be bad on APPEND

1) Differentiate error messages between imaplib.abort and imaplib.error
exceptions in the log.

2) Drop connections in the case of imapobj.error, it also might denote a
   broken connection.

Signed-off-by: Sebastian Spaeth <98dcb2717ddae152d5b359c6ea97e4fe34a29d4c@SSpaeth.de>

frioux/offlineimap,frioux/offlineimap