libndp: close sockfd after using to avoid handle leak
libndp: close sockfd after using to avoid handle leak

Fixes: acccd780df517 ("ndptool: add -T target support")
Signed-off-by: Hangbin Liu <7eef14c73bcfaeccf0ed39fc029ee0e09fbfe9fe@redhat.com>
Signed-off-by: Jiri Pirko <1b548d10035ae428195c41f5d55eedb1437ccd8a@mellanox.com>

jpirko/libndp,jpirko/libndp