setup shunit2.
add nstall_ifcfg_file tests.
add a variable for ifcfg-path.
enable to set fcfg_path with IFCFG_PATH_PREFIX.
add configure_bonding_conf test.
add render_ifcfg_bond_master test.
add install_ifcfg_bond_master test.
add render_ifcfg_bond_slave test.
add install_ifcfg_bond_slave test.
fix teardown for install_bond_xx.
add configure_ifcfg_bond_map test.
add render_ifcfg_bridge test.
add install_ifcfg_bridge test.
add configure_ifcfg_bridge_map test.
add configure_vlan_conf test.
add install_ifcfg_vlan test.
add configure_ifcfg_vlan_map test.
add render_ifcfg_vlan test.
add render_ifcfg_tap test.
add install_ifcfg_tap.sh test.