Introduce 2 APIs to support emulator threads pin.
1) virDomainEmulatorPinAdd: setup emulator threads pin with a given cpumap string.
2) virDomainEmulatorPinDel: remove all emulator threads pin.
Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>