selftests/bpf: Reset process and thread affinity after each test/sub-test

Some tests and sub-tests are setting "custom" thread/process affinity and
don't reset it back. Instead of requiring each test to undo all this, ensure
that thread affinity is restored by test_progs test runner itself.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200314013932.4035712-3-andriin@fb.com

tools/testing/selftests/bpf/test_progs.h

@@ -71,6 +71,7 @@ struct test_env {
 	FILE *stderr;
 	char *log_buf;
 	size_t log_cnt;
+	int nr_cpus;
 
 	int succ_cnt; /* successful tests */
 	int sub_succ_cnt; /* successful sub-tests */