Suppress cgroup error message on sucess startup

Even if qemudStartVMDaemon suceeds, an error was logged such as
'qemuRemoveCgroup:1778 : internal error Unable to find cgroup for'.
This is because qemudStartVMDaemon calls qemuRemoveCgroup to
ensure that old cgroup does not remain. This workaround makes
sense but leaving an error message may confuse users.
* src/qemu/qemu_driver.c: a an option to the function to suppress the
  error being logged

src/qemu/qemu_driver.c

@@ -1924,7 +1924,8 @@ cleanup:
 
 static int qemuRemoveCgroup(virConnectPtr conn,
                             struct qemud_driver *driver,
-                            virDomainObjPtr vm)
+                            virDomainObjPtr vm,
+                            int quiet)
 {
     virCgroupPtr cgroup;
     int rc;
@@ -1934,9 +1935,10 @@ static int qemuRemoveCgroup(virConnectPtr conn,
 
     rc = virCgroupForDomain(driver->cgroup, vm->def->name, &cgroup, 0);
     if (rc != 0) {
-        qemudReportError(conn, NULL, NULL, VIR_ERR_INTERNAL_ERROR,
-                         _("Unable to find cgroup for %s\n"),
-                         vm->def->name);
+        if (!quiet)
+            qemudReportError(conn, NULL, NULL, VIR_ERR_INTERNAL_ERROR,
+                             _("Unable to find cgroup for %s\n"),
+                             vm->def->name);
         return rc;
     }
 
@@ -2303,7 +2305,7 @@ static int qemudStartVMDaemon(virConnectPtr conn,
         return -1;
 
     /* Ensure no historical cgroup for this VM is lieing around bogus settings */
-    qemuRemoveCgroup(conn, driver, vm);
+    qemuRemoveCgroup(conn, driver, vm, 1);
 
     if ((vm->def->ngraphics == 1) &&
         vm->def->graphics[0]->type == VIR_DOMAIN_GRAPHICS_TYPE_VNC &&
@@ -2505,7 +2507,7 @@ cleanup:
         VIR_FREE(vm->def->seclabel.label);
         VIR_FREE(vm->def->seclabel.imagelabel);
     }
-    qemuRemoveCgroup(conn, driver, vm);
+    qemuRemoveCgroup(conn, driver, vm, 0);
     if ((vm->def->ngraphics == 1) &&
         vm->def->graphics[0]->type == VIR_DOMAIN_GRAPHICS_TYPE_VNC &&
         vm->def->graphics[0]->data.vnc.autoport)
@@ -2595,7 +2597,7 @@ static void qemudShutdownVMDaemon(virConnectPtr conn,
     qemuDomainReAttachHostDevices(conn, driver, vm->def);
 
 retry:
-    if ((ret = qemuRemoveCgroup(conn, driver, vm)) < 0) {
+    if ((ret = qemuRemoveCgroup(conn, driver, vm, 0)) < 0) {
         if (ret == -EBUSY && (retries++ < 5)) {
             usleep(200*1000);
             goto retry;