idmap2: fix static checks

Fix two errors detected by static-checks.sh:

  - bpfmt: remove -s flag (sort arrays) since it makes no sense to order
    clang-tidy flags alphabetically: flags must be passed to clang-tidy
    in the order specified to make sense

  - cpplint: allow NOLINT(cert-dcl50-cpp)

Test: cmds/idmap2/static-checks.sh
Change-Id: I6677f8e7504551746edae458acd523e643044c7e