selftests/bpf: fix double bpf_object__close() in veristate

selftests/bpf: fix double bpf_object__close() in veristate

bpf_object__close(obj) is called twice for BPF object files with single
BPF program in it. This causes crash. Fix this by not calling
bpf_object__close() unnecessarily.

Fixes: c8bc5e050976 ("selftests/bpf: Add veristat tool for mass-verifying BPF object files")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220921164254.3630690-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>