As this service is used by the human monitor, make sure that errors get
reported to the right channel, and also raise the verbosity.

This requires to move Monitor typedef in qemu-common.h to resolve the
include dependency.
Signed-off-by: NJan Kiszka <jan.kiszka@siemens.com>
CC: Huang Ying <ying.huang@intel.com>
CC: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
CC: Jin Dongming <jin.dongming@np.css.fujitsu.com>
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>