After an upgrade from 12.04 to 14.04 I got a scared with the message "suckit rootkit detected", too. rkhunter does not find anything. Here is the MD5SUM of my /sbin/init
c9b343f85e6804e2d7ee70b810b1a15a /sbin/init
which is the same as found in /var/lib/dpkg/info/upstart.md5sums.
After an upgrade from 12.04 to 14.04 I got a scared with the message "suckit rootkit detected", too. rkhunter does not find anything. Here is the MD5SUM of my /sbin/init
c9b343f85e6804e 2d7ee70b810b1a1 5a /sbin/init
which is the same as found in /var/lib/ dpkg/info/ upstart. md5sums.