Merge branch 'use network helpers, part 2'

Geliang Tang says:

====================
This patchset uses more network helpers in test_sock_addr.c, but
first of all, patch 2 is needed to make network_helpers.c independent
of test_progs.c. Then network_helpers.h can be included into
test_sock_addr.c without compile errors.

Patch 1 and patch 2 address Martin's comments for the previous series
too.

v2:
 - Only a few minor cleanups to patch 5.
====================

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>