vz: add error code for case if vm is already stopped

If try to stop VM or container which is already stopped than
Virtuozzo 7 returns code PRL_ERR_INVALID_ACTION_REQUESTED.
Error code PRL_ERR_DISP_VM_IS_NOT_STARTED is used in Virtuozzo 6

src/vz/vz_sdk.c

@@ -2050,6 +2050,7 @@ prlsdkDomainChangeStateLocked(vzDriverPtr driver,
         switch (pret) {
         case PRL_ERR_DISP_VM_IS_NOT_STARTED:
         case PRL_ERR_DISP_VM_IS_NOT_STOPPED:
+        case PRL_ERR_INVALID_ACTION_REQUESTED:
             virerr = VIR_ERR_OPERATION_INVALID;
             break;
         default: