roundcube: Implement force_upgrade

Also hold the package during dist upgrade.

Feb 03 19:47:50 mybox upgrades[12262]: Setting up roundcube-core (1.4.10+dfsg.2-1) ...
Feb 03 19:47:50 mybox upgrades[12262]: 
Feb 03 19:47:50 mybox upgrades[12262]: Configuration file '/etc/roundcube/apache.conf'
Feb 03 19:47:50 mybox upgrades[12262]:  ==> Modified (by you or by a script) since installation.
Feb 03 19:47:50 mybox upgrades[12262]:  ==> Package distributor has shipped an updated version.
Feb 03 19:47:50 mybox upgrades[12262]:    What would you like to do about it ?  Your options are:
Feb 03 19:47:50 mybox upgrades[12262]:     Y or I  : install the package maintainer's version
Feb 03 19:47:50 mybox upgrades[12262]:     N or O  : keep your currently-installed version
Feb 03 19:47:50 mybox upgrades[12262]:       D     : show the differences between the versions
Feb 03 19:47:50 mybox upgrades[12262]:       Z     : start a shell to examine the situation
Feb 03 19:47:50 mybox upgrades[12262]:  The default action is to keep your current version.
Feb 03 19:47:50 mybox upgrades[12262]: *** apache.conf (Y/I/N/O/D/Z) [default=N] ? dpkg: error processing>
Feb 03 19:47:50 mybox upgrades[12262]:  end of file on stdin at conffile prompt
Feb 03 19:47:50 mybox upgrades[12262]: Setting up python3-radicale (3.0.6-1) ...
Feb 03 19:47:51 mybox upgrades[12262]: dpkg: dependency problems prevent configuration of roundcube:
Feb 03 19:47:51 mybox upgrades[12262]:  roundcube depends on roundcube-core (= 1.4.10+dfsg.2-1); however:
Feb 03 19:47:51 mybox upgrades[12262]:   Package roundcube-core is not configured yet.
Feb 03 19:47:51 mybox upgrades[12262]: 
Feb 03 19:47:51 mybox upgrades[12262]: dpkg: error processing package roundcube (--configure):
Feb 03 19:47:51 mybox upgrades[12262]:  dependency problems - leaving unconfigured