NODECTRL: Fix some problems with logging and callbacks

- The widgets do not have a logger itself, the node logger has to be
  used
- The 'target_go' callback function has to be part of the Driveable
  widget not the Readable widget

Change-Id: Ie045fb02414d768fcf9c5e3f8590267209e23d83
Reviewed-on: https://forge.frm2.tum.de/review/17721
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>

secop/gui/nodectrl.py

@@ -229,7 +229,7 @@ class ReadableWidget(QWidget):
             val = self._node.getParameter(self._module, pname)[0]
             return val
         except Exception:
-            self.log.exception()
+            self._node.log.exception()
             if fallback is not Ellipsis:
                 return fallback
             raise
@@ -260,14 +260,6 @@ class ReadableWidget(QWidget):
     def update_target(self, target, qualifiers=None):
         pass
 
-    def target_go(self, target):
-        print self, target
-        try:
-            self._node.setParameter(self._module, 'target', target)
-        except Exception as e:
-            self.log.exception(e)
-            QMessageBox.warning(self.parent(), 'Operation failed', str(e))
-
     def _updateValue(self, module, parameter, value):
         if module != self._module:
             return
@@ -313,6 +305,14 @@ class DrivableWidget(ReadableWidget):
         else:
             self.targetLineEdit.setText(str(target))
 
+    def target_go(self, target):
+        print self, target
+        try:
+            self._node.setParameter(self._module, 'target', target)
+        except Exception as e:
+            self._node.log.exception(e)
+            QMessageBox.warning(self.parent(), 'Operation failed', str(e))
+
     def on_cmdPushButton_clicked(self, toggle=False):
         if toggle:
             return