qemu: improve error for failed JSON commands
qemu: improve error for failed JSON commands

Only one error in qemu_monitor was already using the relatively
new OPERATION_UNSUPPORTED error, even though it is a better fit
for all of the messages related to options that are unsupported
due to the version of qemu in use rather than due to a user's
XML or .conf file choice.  Suggested by Osier Yang.

* src/qemu/qemu_monitor.c (qemuMonitorSendFileHandle)
(qemuMonitorAddHostNetwork, qemuMonitorRemoveHostNetwork)
(qemuMonitorAttachDrive, qemuMonitorDiskSnapshot)
(qemuMonitorDriveMirror, qemuMonitorTransaction)
(qemuMonitorBlockCommit, qemuMonitorDrivePivot)
(qemuMonitorBlockJob, qemuMonitorSystemWakeup)
(qemuMonitorGetVersion, qemuMonitorGetMachines)
(qemuMonitorGetCPUDefinitions, qemuMonitorGetCommands)
(qemuMonitorGetEvents, qemuMonitorGetKVMState)
(qemuMonitorGetObjectTypes, qemuMonitorGetObjectProps)
(qemuMonitorGetTargetArch): Use better error category.

olafhering/libvirt,siboulet/libvirt-openvz,trainstack/libvirt,crobinso/libvirt,libvirt/libvirt,bjzhang/libvirt,emaste/libvirt,VenkatDatta/libvirt,olafhering/libvirt,zippy2/libvirt,elmarco/libvirt,andreabolognani/libvirt,jeckersb/libvirt,nertpinx/libvirt,emaste/libvirt,iam-TJ/libvirt,rlaager/libvirt,agx/libvirt,nertpinx/libvirt,datto/libvirt,zippy2/libvirt,cbosdo/libvirt,zhlcindy/libvirt-1.1.4-maintain,rlaager/libvirt,agx/libvirt,nertpinx/libvirt,jardasgit/libvirt,rlaager/libvirt,crobinso/libvirt,trainstack/libvirt,VenkatDatta/libvirt,crobinso/libvirt,VenkatDatta/libvirt,emaste/libvirt,VenkatDatta/libvirt,taget/libvirt,jeckersb/libvirt,agx/libvirt,rlaager/libvirt,emaste/libvirt,jeckersb/libvirt,jeckersb/libvirt,jfehlig/libvirt,shugaoye/libvirt,andreabolognani/libvirt,taget/libvirt,jeckersb/libvirt,eskultety/libvirt,trainstack/libvirt,bjzhang/libvirt,eskultety/libvirt,iam-TJ/libvirt,elmarco/libvirt,zippy2/libvirt,taget/libvirt,fabianfreyer/libvirt,emaste/libvirt,cbosdo/libvirt,datto/libvirt,trainstack/libvirt,taget/libvirt,rlaager/libvirt,shugaoye/libvirt,olafhering/libvirt,fabianfreyer/libvirt,datto/libvirt,datto/libvirt,fabianfreyer/libvirt,elmarco/libvirt,elmarco/libvirt,fabianfreyer/libvirt,agx/libvirt,siboulet/libvirt-openvz,eskultety/libvirt,jardasgit/libvirt,taget/libvirt,siboulet/libvirt-openvz,libvirt/libvirt,bjzhang/libvirt,fabianfreyer/libvirt,cbosdo/libvirt,nertpinx/libvirt,trainstack/libvirt,emaste/libvirt,shugaoye/libvirt,trainstack/libvirt,crobinso/libvirt,andreabolognani/libvirt,zhlcindy/libvirt-1.1.4-maintain,cbosdo/libvirt,datto/libvirt,zhlcindy/libvirt-1.1.4-maintain,jardasgit/libvirt,zhlcindy/libvirt-1.1.4-maintain,andreabolognani/libvirt,emaste/libvirt,nertpinx/libvirt,eskultety/libvirt,jardasgit/libvirt,iam-TJ/libvirt,trainstack/libvirt,siboulet/libvirt-openvz,olafhering/libvirt,VenkatDatta/libvirt,siboulet/libvirt-openvz,shugaoye/libvirt,libvirt/libvirt,iam-TJ/libvirt,bjzhang/libvirt,bjzhang/libvirt,elmarco/libvirt,agx/libvirt,eskultety/libvirt,zhlcindy/libvirt-1.1.4-maintain,jfehlig/libvirt,iam-TJ/libvirt,jeckersb/libvirt,jeckersb/libvirt,jfehlig/libvirt,zippy2/libvirt,iam-TJ/libvirt,jfehlig/libvirt,iam-TJ/libvirt,shugaoye/libvirt,libvirt/libvirt,andreabolognani/libvirt,cbosdo/libvirt,jardasgit/libvirt