Pkg or dbus should create /etc/machine-id when not found

[scratch65535 at att.net]

Not only that, but pkg should not delete things until AFTER it
successfully replaces them!

I finally broke down and did a pkg upgrade yesterday, which cost
me the whole afternoon.  I had to do it because pkg wasn't smart
enough not to use the current quarter's bits to install a package
on a machine that was using the original 10.3 RELEASE bits.  (If
that's to be considered normal behavior, then not only are we all
forced to update every time the minor version changes, we have to
disruptively update every quarter unless we forego installing
anything new.  I realise that, when you're up to your arse in
alligators draining the swamp isn't uppermost in your mind, but
there really are people for whom freebsd is a *tool*, not a hobby
or a way to commit suicide by exhaustion.) 

This disruption involved pkg deleting Firefox (why?) because I
was trying to install VLC (which turned out to be broken).  When
I tried to restore Firefox, I got bitten by quarterly version
skew.

So this morning, despite the sacrifice of the half-day yesterday,
X failed to start because dbus couldn't find /etc/machine-id, a
file it never wanted to find before now.  Since the fix seems
easy enough:  call dbus-uuidgen --ensure=/etc/machine-id, it's
hard to know why pkg or dbus doesn't generate it when it can't
find it.  I filed a bug.