Set debug log level for error attempts of getting user stacktrace

Signed-off-by: Andrey Fedotov <anfedotoff@yandex-team.ru>

pkg/sensors/tracing/generickprobe.go

@@ -1110,7 +1110,7 @@ func handleMsgGenericKprobe(m *api.MsgGenericKprobe, gk *genericKprobe, r *bytes
 			logger.GetLogger().Warnf("failed to retrieve kernel stacktrace: id equal to errno %d", m.KernelStackID)
 		}
 		if m.UserStackID < 0 {
-			logger.GetLogger().Warnf("failed to retrieve user stacktrace: id equal to errno %d", m.UserStackID)
+			logger.GetLogger().Debugf("failed to retrieve user stacktrace: id equal to errno %d", m.UserStackID)
 		}
 		if gk.data.stackTraceMap.MapHandle == nil {
 			logger.GetLogger().WithError(err).Warn("failed to load the stacktrace map")