cgroup_id_map: change example for CGRP_STORAGE to not use GET_F_CREATE

[dqminh]

BPF_LOCAL_STORAGE_GET_F_CREATE will create a zero entry if it does not find our cgroup in the CGRP_STORAGE. THis is unnecessary work as the entry should only be written by ebpf_exporter for cgroups that we are interested in, so we should not set the flag.

[netoptimizer]

Have you seen: https://github.com/netoptimizer/ebpf_exporter/pull/1#discussion_r2305190268

• I found that this CGRP_STORAGE was slower than the hash type