selftests/bpf: test_verifier verbose causes erroneous failures

selftests/bpf: test_verifier verbose causes erroneous failures

When running test_verifier with the -v flag and a test with
`expected_ret==VERBOSE_ACCEPT`, the opts.log_level is unintentionally
overwritten because the verbose flag takes precedence. This leads to
a mismatch in the expected and actual contents of bpf_vlog, causing
tests to fail incorrectly.

Reorder the conditional logic that sets opts.log_level to preserve
the expected log level and prevent it from being overridden by -v.

Signed-off-by: Gregory Bell <grbell@redhat.com>
Link: https://lore.kernel.org/r/182bf00474f817c99f968a9edb119882f62be0f8.1747058195.git.grbell@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>