Comment 10 for bug 1417037

Same problem here on 14.04.2, Andrei's comment did not help either:

root@user:~# /bin/sh /var/lib/dpkg/info/rsyslog.postinst configure 7.4.4-1ubuntu2.3
The user `syslog' is already a member of `adm'.
/usr/bin/deb-systemd-helper was not called from dpkg. Exiting.
/usr/bin/deb-systemd-helper was not called from dpkg. Exiting.
/usr/bin/deb-systemd-helper was not called from dpkg. Exiting.
Skipping profile in /etc/apparmor.d/disable: usr.sbin.rsyslogd
invoke-rc.d: initscript rsyslog, action "restart" failed.

root@user:~# apt-get -f install
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 15 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Setting up rsyslog (7.4.4-1ubuntu2.5) ...
The user `syslog' is already a member of `adm'.
Skipping profile in /etc/apparmor.d/disable: usr.sbin.rsyslogd
invoke-rc.d: initscript rsyslog, action "restart" failed.
dpkg: error processing package rsyslog (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 rsyslog
E: Sub-process /usr/bin/dpkg returned an error code (1)