add action reset image permission

- reset volume image uid:gid to owner

libvirt should revert its owner to original user
but it has never been implemented yet.
This is work around for it.

Signed-off-by: Hiroshi Miura <miurahr@linux.com>
util: introduce run_root_command()

-prepare separate run_command() for root previleges.

TODO: some host OS need to use 'su -c' instead of 'sudo'

Signed-off-by: Hiroshi Miura <miurahr@linux.com>
Merge pull request #152 from miurahr/avoid_libvirt_security_bug

Avoid libvirt security bug