MFC r314830:

MFC r314830:

mergemaster: fix description of -p

-p only handles updating /etc/master.passwd and /etc/group . No more,
no less.

Also, mergemaster (and no other portions of the vanilla FreeBSD build
process) should be messing with __MAKECONF or SRCCONF as part of the
installworld or distribution process. Don't insinuate that mergemaster
does that as it's a false claim.

git-svn-id: svn://svn.freebsd.org/base/stable/10@315343 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f