qemu: monitor: clear cpu props properly in CPUInfoClear

Stay true to the name of the function and clear the pointer
after freeing it.

This also silences a bogus Coverity report about a double
free in qemuMonitorGetCPUInfo where qemuMonitorCPUInfoClear
is called right after allocating a new qemuMonitorCPUInfo
to fill out the non-zero defaults.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>

src/qemu/qemu_monitor.c

@@ -1661,6 +1661,7 @@ qemuMonitorCPUInfoClear(qemuMonitorCPUInfoPtr cpus,
         VIR_FREE(cpus[i].alias);
         VIR_FREE(cpus[i].type);
         virJSONValueFree(cpus[i].props);
+        cpus[i].props = NULL;
     }
 }