Look for custom initscripts in /etc/init.d

While RHEL symlinks /etc/init.d to /etc/rc.d/init.d, /etc/init.d is the
path typically referenced, and indeed /sbin/service looks directly in
/etc/init.d. This commit will account for the corner-case where a distro
does not symlink /etc/init.d to /etc/rc.d/init.d/.