hmp: change hmp_info_cpus to use query-cpus-fast

hmp: change hmp_info_cpus to use query-cpus-fast

Changing the implementation of hmp_info_cpus() to call
qmp_query_cpus_fast() instead of qmp_query_cpus. This has the
following consequences:

  o No further code change required for qmp_query_cpus deprecation

  o HMP profits from the less disruptive cpu information retrieval

  o HMP 'info cpus' won't display architecture specific data anymore,
    which should be tolerable in the light of the deprecation of
    query-cpus.

In order to allow 'info cpus' to be executed completely on the
fast path, monitor_get_cpu_index() has been adapted to not synchronize
the cpu state.

Signed-off-by: Viktor Mihajlovski <[email protected]>
Message-Id: <1518797321[email protected]>
Reviewed-by: Cornelia Huck <[email protected]>
Reviewed-by: Eric Blake <[email protected]>
Signed-off-by: Cornelia Huck <[email protected]>