* src/qemu/qemu_monitor_text.c: BALLOON_PREFIX was defined as
"balloon: actual=", which cause "actual=" is stripped early before
the real parsing. This patch changes BALLOON_PREFIX into "balloon: ",
and modifies related functions, also renames
"qemuMonitorParseExtraBalloonInfo" to "qemuMonitorParseBalloonInfo",
as after the changing, it parses all the info returned by "info balloon".