tools/bpf: adjust rlimit RLIMIT_MEMLOCK for test_verifier_log

The default rlimit RLIMIT_MEMLOCK is 64KB. In certain cases,
e.g. in a test machine mimicking our production system, this test may
fail due to unable to charge the required memory for prog load:
  # ./test_verifier_log
  Test log_level 0...
  ERROR: Program load returned: ret:-1/errno:1, expected ret:-1/errno:22

Changing the default rlimit RLIMIT_MEMLOCK to unlimited makes
the test always pass.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>