OS-2211: Change the default metadata sock permisisons.

Change the file permission to be 0700 after the socket is created.
OS-2218 'imgadm list' misses incremental images
OS-2222 make reprovision more robust by forcing zfs renames and undoing transition if we fail.
OS-2223 don't fail reprovision when /zones/<uuid>/cores is not mounted.
OS-2213 switch metadata agent to using internal_metadata for *_pw keys to support older datasets.
OS-2224: imgadm "-E" option for machine parsable error
OS-2211: Set umask instead of chmod'ing, set metdata.sock smartdc directory usable only by root
Merge branch 'master' of git://github.com/joyent/smartos-live into ec