qemu: Free saved error in qemuDomainSetVcpusFlags

Commit e3435caf added cleanup code to qemuDomainSetVcpusFlags() that was
not supposed to reset the error.  Usual procedure was done, saving the
error to temporary variable, but it was never free'd, but rather leaked.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

src/qemu/qemu_driver.c

@@ -4781,6 +4781,7 @@ qemuDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
         err = virSaveLastError();
         virCgroupSetCpusetMems(cgroup_temp, mem_mask);
         virSetError(err);
+        virFreeError(err);
     }
 
     if (!qemuDomainObjEndJob(driver, vm))