qemu: Allow enabling/disabling features with host-passthrough

QEMU supports feature specification with -cpu host and we just skip
using that.  Since QEMU developers themselves would like to use this
feature, this patch modifies the code to work.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1178850

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>

tests/qemuxml2xmltest.c

@@ -184,6 +184,7 @@ mymain(void)
     DO_TEST("clock-localtime");
     DO_TEST("cpu-kvmclock");
     DO_TEST("cpu-host-kvmclock");
+    DO_TEST("cpu-host-passthrough-features");
     DO_TEST("clock-catchup");
     DO_TEST("kvmclock");
     DO_TEST("clock-timer-hyperv-rtc");