The support for <boot rebootTimeout="12345"/> was added before we were
checking for qemu command line options in QMP, so we haven't properly
adapted virQEMUCaps when using it and thus we report unsupported
option with new enough qemu.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1042690Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>