Fix #1079588 by not outputting to stdout in maintainer scripts
From The Debconf Programmer's Tutorial: "Anything your maintainer scripts output to standard output is passed into the frontend as a command". We must make sure to redirect stdout to stderr for every command in the postinst and postrm scripts which might output to stdout.
* debian/mandos-client.postinst (update_initramfs): Add "1>&2" to invocations of update-initramfs and /etc/kernel/postinst.d/dracut. (add_mandos_user): Add "1>&2" to invocations of usermod, groupmod, and adduser. (create_keys): Add "1>&2" to invocations of mandos-keygen, gpg-connect-agent, certtool, and openssl. (create_dh_params): Add "1>&2" to invocations of certtool and openssl. Add "--force" option to "rm". * debian/mandos-client.postrm (update_initramfs): Add "1>&2" to invocations of update-initramfs and /etc/kernel/postinst.d/dracut.
Closes: #1079588 Reported-By: Ben Hutchings <ben@decadent.org.uk>