different behavior when called as "mailq" then "/usr/bin/mailq"

[Mask66]

We ran into problems calling dma (on FreeBSD) from the nagios check_mailq script, and found out that it behaves correctly when called as just "mailq", but incorrectly when called as "/usr/bin/mailq" (with a path) for example. This patch (see pull request #52) written by my colleague Klaus-Uwe Ittner corrects this.

Also reported as https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=216910.

[corecode]

commited, thanks!