bin/60524: mtree tumbles on files begining with hashmark(#)

[Hiroharu Tamaru]

Hello committers,

Could someone take time and look into this PR?
It has been left unattended for some time now, and phk obviously seems
quite busy on other projects.
I'd appreciate if one of the commiters could review and MFC it.
A patch to -stable is enclosed in the PR.
Thanks in advance.

http://www.freebsd.org/cgi/query-pr.cgi?pr=60524

Please keep me in the CC. I'm not subscribed to the stable list.
-- 
Hiroharu Tamaru