qemu: remove redundant virQEMUDriverGetConfig

qemuDomainSetSchedulerParametersFlags() calls virQEMUDriverGetConfig() twice
and makes the reference counter leak. This removes redundant call.

Problem introduced in commit 45ad1adbSigned-off-by: NEric Blake <eblake@redhat.com>

src/qemu/qemu_driver.c

@@ -9050,7 +9050,6 @@ qemuDomainSetSchedulerParametersFlags(virDomainPtr dom,
     if (virDomainSetSchedulerParametersFlagsEnsureACL(dom->conn, vm->def, flags) < 0)
         goto cleanup;
 
-    cfg = virQEMUDriverGetConfig(driver);
     if (!cfg->privileged) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                        _("CPU tuning is not available in session mode"));