pbulk: implement chroot support better.

This allows proper creation/deletion of chroots in a timely manner
prior to starting the clients, and avoids race conditions.  Also
start to add various sections to the example configuration file ready
for merging upstream.
pbulk: background the right parts.
Backport graphics/edje PLIST fix.
PLIST fix for graphics/gimp.
Build fix for graphics/shotwell.
Merge branch 'joyent/feature/miscfix/2013Q2' into joyent/release/2013Q2