Fcron: Disable checks for root{name,group} and others.

This fixes building fcron. It was complaining it couldn't check root's
user name and the suggested flag (--with-rootname) didn't do anything.

Signed-off-by: Moritz Ulrich <moritz@tarn-vedra.de>
Merge pull request #878 from the-kenny/fix-fcron

Fcron: Disable checks for root{name,group} and others.