tools/bpftool: move set_max_rlimit() before __bpf_object__open_xattr()

tools/bpftool: move set_max_rlimit() before __bpf_object__open_xattr()

For a host which has a lower rlimit for max locked memory (e.g., 64KB),
the following error occurs in one of our production systems:
  # /usr/sbin/bpftool prog load /paragon/pods/52877437/home/mark.o \
    /sys/fs/bpf/paragon_mark_21 type cgroup/skb \
    map idx 0 pinned /sys/fs/bpf/paragon_map_21
  libbpf: Error in bpf_object__probe_name():Operation not permitted(1).
    Couldn't load basic 'r0 = 0' BPF program.
  Error: failed to open object file

The reason is due to low locked memory during bpf_object__probe_name()
which probes whether program name is supported in kernel or not
during __bpf_object__open_xattr().

bpftool program load already tries to relax mlock rlimit before
bpf_object__load(). Let us move set_max_rlimit() before
__bpf_object__open_xattr(), which fixed the issue here.

Fixes: 47eff61777c7 ("bpf, libbpf: introduce bpf_object__probe_caps to test BPF capabilities")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>