When converting QEMU argv into a virDomainDefPtr, also extract
the pidfile, monitor character device config and the monitor
mode.

* src/qemu/qemu_command.c, src/qemu/qemu_command.h: Extract
  pidfile & monitor config from QEMU argv
* src/qemu/qemu_driver.c, tests/qemuargv2xmltest.c: Add extra
  params when calling qemuParseCommandLineString