K 10
svn:author
V 6
emaste
K 8
svn:date
V 27
2018-02-28T17:20:10.043136Z
K 7
svn:log
V 381
rc.d/jail: avoid misinterpreting expr arguments

(Due to some misconfiguration) I ended up with _mask set to
"-v<something>", and /etc/rc.d/jail then failed with
"expr: illegal option -- v".

Use "expr --" so that variable content is never interpreted as an
option.

Reviewed by:	jamie
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D14535

END