oops.  made a race condition already :)

Well that was silly, buildit.sh races docker in the (untested)
background mode to put the dockerfile back the way it started.

Solving this correctly is shockingly hard.  Maybe backgrounding
isn't worth it or something?

For now kludge while I think it over.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
prov.sh: fix etc-update bug, make optional

o etc-update was still failing due to a bashscript
  thinko.  Fixed by grouping commands correctly.

o It might be useful to be able to use
  PROV_NO_OVERRIDE_CONFIG_PROTECT (thus keeping the
  CONFIG_PROTECT defaults, while still auto-discarding
  the changes (thus making everything in CONFIG_PROTECT
  effectively immutable).  To allow this, I added PROV_NO_UPDATE;
  so that putting a non-empty value into both
  PROV_NO_OVERRIDE_CONFIG_PROTECT and PROV_NO_ETC_UPDATE
  will achieve this result.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
Dockerfile: be much less verbose while cleaning up.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
Dockerfile: fix the onbuild run invocation to actually work.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
Dockerfile: remove more stuff at the end

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>
Dockerfile: remove the volume export

I'm not using this yet and don't yet have a full grasp of the implications
so drop it for now.

Signed-off-by: Gregory M. Turner <gmt@be-evil.net>