Include failed message if monit.d is empty

[Former user]

monit should not report a failed message if a monitrc include of /etc/monit.d/* is empty.

/etc/monitrc:167: Include failed -- Success '/etc/monit.d/*'

such .d directories are usually for dynamic changes for service config files, thus an empty directory is OK

[Tildeslash]

Duplicate of #438.