Roundcube webmail uses again 127.0.0.1 as IMAP server

This was changed due to a Openchange policy added to Dovecot that
allowed any user from localhost to login against the IMAP server
without a correct password (also Roundcube)
Merge pull request #1443 from Zentyal/mjulian/webmail-imap-again-to-localhost

Roundcube webmail uses again 127.0.0.1 as IMAP server