various fixes

- nodestatechange callback must appear after the online attribute
  is changed
- IntRange: move range validation outside of try except
- fixes on some error names
- well defined error message 'no such class' in secop.lib.get_class
- try again 4 times when starting Tcp Server on EADDRINUSE
- fix error handling

Change-Id: I4eee9b79ea8173936b9f5193b87e006ac8fca827
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/26171
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

secop/poller.py

@@ -202,7 +202,7 @@ class Poller(PollerBase):
                 module.pollOneParam(pname)
                 done = True
                 lastdue = due
-                due = max(lastdue + mininterval, now + min(self.maxwait, mininterval * 0.5))
+            due = max(lastdue + mininterval, now + min(self.maxwait, mininterval * 0.5))
             # replace due, lastdue with new values and sort in
             heapreplace(queue, (due, lastdue, pollitem))
         return 0
@@ -227,9 +227,10 @@ class Poller(PollerBase):
         (where n is the number of regular parameters).
         """
         if not self:
-            # nothing to do (else we might call time.sleep(float('inf')) below
+            # nothing to do (else time.sleep(float('inf')) might be called below
             started_callback()
             return
+        # if writeInitParams is not yet done, we do it here
         for module in self.modules:
             module.writeInitParams()
         # do all polls once and, at the same time, insert due info