Improve E255 handling:

- start BackgroundTask on first data not valid
 - in any case of E255/data-no-valid: try to restart diag;
   This is because there were only 'returns' without initiating
   something, so that next check/restart carun happened first on next
   wokeup.

src/ATBAPP/DeviceControllerDiag.cpp

@@ -112,6 +112,8 @@ void DeviceControllerDiag::private_startDiag()
         this->flagInterruptDiag = false;
         if (this->E255counter > 5) {
             this->restartCArun();
+            // try it again, until success:
+            QTimer::singleShot(1000, this, &DeviceControllerDiag::diagRequest);
         }
         else {
             this->E255counter++;
@@ -137,8 +139,14 @@ void DeviceControllerDiag::private_startDiag()
     else {
         qCritical() << "DeviceControllerDiag::private_startDiag() DCdata is +++not+++ valid";
 
-        // try it again
         hw->dc_autoRequest(true);
+
+        if (! this->isDiagBackgroundTask) {
+            this->isDiagBackgroundTask = true;
+            this->dbus->startBackgroundTask("E255");
+        }
+
+        // try it again
         QTimer::singleShot(200, this, &DeviceControllerDiag::private_startDiag);
     }
 }
@@ -161,6 +169,7 @@ void DeviceControllerDiag::sys_superviseSystem()
         this->isRequestRunning  = false;
         if (this->E255counter > 5) { this->restartCArun(); }
                               else { this->E255counter++; }
+        QTimer::singleShot(400, this, &DeviceControllerDiag::diagRequest);
         return;
     }
 
@@ -174,6 +183,7 @@ void DeviceControllerDiag::sys_superviseSystem()
         this->isRequestRunning  = false;
         if (this->E255counter > 5) { this->restartCArun(); }
                               else { this->E255counter++; }
+        QTimer::singleShot(400, this, &DeviceControllerDiag::diagRequest);
         return;
     }
 
@@ -439,6 +449,11 @@ void DeviceControllerDiag::sub_componentAssessment()
 
     this->previousMachineEventSet = machineEventSet;
     this->machineEventSet.clear();
+
+    if (this->isDiagBackgroundTask) {
+        this->isDiagBackgroundTask = false;
+        this->dbus->finishedBackgroundTask("E255");
+    }
 }