vz: fix handle leak in prlsdkHandleVmStateEvent

Every successful call of PrlEvent_GetParamByName allocates a handle,
which has to be freed.

Signed-off-by: Maxim Nestratov <mnestratov@virtuozzo.com>

src/vz/vz_sdk.c

@@ -2147,6 +2147,7 @@ prlsdkHandleVmStateEvent(vzDriverPtr driver,
     prlsdkSendEvent(driver, dom, lvEventType, lvEventTypeDetails);
 
  cleanup:
+    PrlHandle_Free(eventParam);
     virObjectUnlock(dom);
     return;
 }