pgsql: If query fails because connection gets closed, return a proper error message.
pgsql: If query fails because connection gets closed, return a proper error message.

--HG--
branch : HEAD

jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot