Remove references to STAGEDIR which is no longer used.

(cherry picked from commit 31cfd34f5351bed4082c9f3af308d1ec34f298eb)
Add /rescue to PATH in a few early startup scripts on ISO.

(cherry picked from commit f1c6b79310c60b8e6577f72f9bea0332af6808da)
Add /tank directory to UFS install image on ISO.  This will be used as a mountpoint for a zpool named tank.

(cherry picked from commit 93dcbaf16bf31ec10c596ffb738e6c4d7a8ff680)
Be more explicit about what binaries we copy to the UFS install image on the ISO.
Recent changes in FreeBSD/src/rescue/rescue/Makefile removed dialog
from /rescue, so we ended up not installing dialog.
This broke the install.

In future we will replace all these invocations of cp
with a manifest file.

(cherry picked from commit cd79454174c73dcb39235d89cfa7540b0768a02d)
Add xargs

(cherry picked from commit 4783e66d09c481de9bbb677c1229c63da3d162b5)
If we booted off of an NFS root via PXE, then do not tell user to remove CD-ROM on reboot.

(cherry picked from commit 111724075df28897735dd85087e8d6249bd6c402)
If it exists in /rescue, create a symlink in one of the
/bin directories for compatibility with scripts.
Copy in binaries we need, such as dialog.
Create additional symlinks.
Remove the /boot directory from inside the UFS install image.  It is not needed.
The outer ISO which we boot from already contains the /boot directory.
Create a symlink from /boot to /.mount/boot so that at least from
inside the UFS install image, we can see the outer /boot directory in the ISO.