mon: structure 'ceph status' json output

Return the summary info in a structured for instead of just mimicing the
legacy plaintext format.

Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Joao Eduardo Luis <joao.luis@inktank.com>
msgr: add 'ms die on old message' to help catch reconnect seq issues

Signed-off-by: Sage Weil <sage@inktank.com>