[Setup] Move a condition into install_container_config() function.
[Sample] Update sample.
[Setup] Install configuration file of container, even if the value is
defined in the configuration file, the value will be updated.
[Setup] Fix a sentence.
[Setup] Add two functions to install ifcfg-eth0 file.

- prepare_install_ifcfg_eth0_file()
- install_ifcfg_eth0_file()
[Setup] Remove commented out lines.