[libvirt] add ivshmem property master

[Problem Description] I read qemu-doc.texi in qemu-mster source code, which have a explain of migrating ivshmem below “With device property @option{master=on}, the guest will copy the shared.memory on migration to the destination host. With @option{master=off}, the guest will not be able to migrate with the device attached.” However, libvirt library can not recognize the property “master=on”. When I directly used command "qemu-kvm -device ivshmem-plain,id=shmem0,memdev=shmmem-shmem0,master=on,bus=pci.0,addr=0xa” to launch a guest, qemu support ivshmem property master=on. So, I suggest adding code to support property master=on in libvirt. [Code Review] The below is the part of source code in qemu-master. There's no definition here about ivshmem master. domain_conf.h struct _virDomainShmemDef { char *name; unsigned long long size; int model; /* enum virDomainShmemModel */ struct { bool enabled; virDomainChrSourceDef chr; } server; struct { bool enabled; unsigned vectors; virTristateSwitch ioeventfd; } msi; virDomainDeviceInfo info; }; [changed code] src/conf/domain_conf.c src/conf/domain_conf.h [Detail of Source Code Modification] src/conf/domain_conf.h [cid:image001.png@01D4BA48.57FBFA10] src/conf/domain_conf.c [cid:image002.png@01D4BA48.5B8017C0]