selftests: bpf: Fix bind on used port

selftests: bpf: Fix bind on used port

[ Upstream commit 8c0be0631d81e48f77d0ebf0534c86e32bef5f89 ]

The bind_perm BPF selftest failed when port 111/tcp was already in use
during the test. To fix this, the test now runs in its own network name
space.

To use unshare, it is necessary to reorder the includes. The style of
the includes is adapted to be consistent with the other prog_tests.

v2: Replace deprecated CHECK macro with ASSERT_OK

Fixes: 8259fdeb30326 ("selftests/bpf: Verify that rebinding to port < 1024 from BPF works")
Signed-off-by: Felix Maurer <fmaurer@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/551ee65533bb987a43f93d88eaf2368b416ccd32.1642518457.git.fmaurer@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>