A number of RPC functions have no apparent callers in any
of the expected call sites.  That is, they appear to be
unused as RPC functions.

The following are probably entirely unused, and should be
considered for deletion:
    add_test
    add_user
    delete_test
    delete_user
    get_host_history
    modify_acl_group
    modify_test

The following may be used as ordinary functions (not RPC
end points).  These should either be made private to their
module, or moved to someplace like rpc_utils.py:
    canonicalize_suite_name
    formatted_now
    get_host_num_special_tasks
    get_test_control_files_by_build
    get_tests_status_counts_by_job_name_label