[th/va-args-join] change implementation of `NM_UTILS_{LOOKUP,ENUM2STR}_DEFINE()`
this is to avoid a lgtm.com warning:
https://lgtm.com/projects/g/NetworkManager/NetworkManager/?mode=tree&ruleFocus=1506698658528
this is to avoid a lgtm.com warning:
https://lgtm.com/projects/g/NetworkManager/NetworkManager/?mode=tree&ruleFocus=1506698658528