Increase QMPClient read buffer limit
Based on the discussion https://www.mail-archive.com/qemu-devel@nongnu.org/msg920953.html, the read buffer limit should be the same as libvirt's default (10 MB)
Based on the discussion https://www.mail-archive.com/qemu-devel@nongnu.org/msg920953.html, the read buffer limit should be the same as libvirt's default (10 MB)