Pass up the error status of minidumpsys() to its callers.

PR:		193761
Submitted by:	Conrad Meyer <conrad.meyer@isilon.com>
Sponsored by:	EMC / Isilon Storage Division


git-svn-id: svn+ssh://svn.freebsd.org/base/head@272766 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f