kdig: add TLS support

src/utils/common/netio.c

src/utils/common/netio.h

src/utils/common/params.h

src/utils/kdig/kdig_exec.c

src/utils/kdig/kdig_params.c

src/utils/kdig/kdig_params.h

src/utils/knsupdate/knsupdate_exec.c