lxc/utils: improve choose_init code readability

Signed-off-by: Silvio Fricke <silvio.fricke@gmail.com>
Merge pull request #353 from ashtoreth/master

added container:attach() into the Lua API
Merge pull request #356 from silvio/sfr/utils-choose-init

lxc/utils: improve choose_init code readability
Merge branch 'lxc-master'