qemu: log the crash information for S390

qemu: log the crash information for S390

Since QEMU 2.12 commit id '4ada99ade' guest crash information for
S390 is available in the QEMU monitor, e.g.:

  {
    "timestamp": {
        "seconds": 1518004739,
        "microseconds": 552563
    },
    "event": "GUEST_PANICKED",
    "data": {
        "action": "pause",
        "info": {
            "core": 0,
            "psw-addr": 1102832,
            "reason": "disabled-wait",
            "psw-mask": 562956395872256,
            "type": "s390"
        }
    }
  }

Let's log this information into the domain log file, e.g.:

    2018-02-08 13:11:26.075+0000: panic s390: core='0' psw-mask='0x0002000180000000' psw-addr='0x000000000010f146' reason='disabled-wait'

Reviewed-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
Signed-off-by: Bjoern Walk <bwalk@linux.vnet.ibm.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>