MFC r273093, r273096:

r273093:
  Merge the following from ^/projects/release-vmimage:
  r272436, r272437, r272792:

  r272436:
    Remove the first argument to panic(), which was initially
    intended to be the exit code, however when a non-zero exit
    code was returned to release/Makefile, this would prevent
    any remaining (and possibly successful) stages from being
    attempted.

  r272437:

    If the vm-base target fails, prevent the vm-image target
    from being run since it cannot possibly succeed.

  r272792:

    Add /usr/local/bin and /usr/local/sbin to PATH, needed
    if third-party software needs to use utilities outside
    of the base system during post-install stages (indexinfo
    is one culprit).

r273096:
  Merge the following from ^/projects/release-vmimage:
  r273076, r273077, r273079, r273095:

  r273076:
    Add a separate make(1) target to release/Makefile to
    build FreeBSD virtual machine disk images for use on
    the Microsoft Azure service.

    For now, this target is not directly connected to the
    build, however can be manually invoked.

    The 'vm-azure' target invokes {amd64,i386}/mk-azure.sh,
    which does the heavy lifting to produce proper VHDs.
    mk-azure.sh uses a configuration file, defaulting to
    tools/azure.conf if otherwise unset.

  r273077:
    Clear VM_RC_LIST.

  r273079:
    Fix signal list to trigger umount(8).

  r273095:
    Output an informational message when mkimg(1) runs, so it
    does not appear that the process has stopped while waiting
    for a 'y/n' response when waagent is deprovisioned.

Relnotes:	yes
Sponsored by:	The FreeBSD Foundation