bsdinstall: Copy in all keys
The keys used for pkgbase signing are going to be placed in
/usr/share/keys/pkgbase-N where N is the FreeBSD major version
number; as such it's not sufficient to copy /usr/share/keys/pkg
into the install chroot, but instead we need /usr/share/keys/*.
With hat: re
MFC after: 8 hours (needed in 15.0-RC1)
Differential Revision: https://reviews.freebsd.org/D53753