improve poller error handling

- repeated errors on poller are only once logged (per poll
  function / read_* method)
- during exception handling, silent=True on a SECoP error indicates
  that the error is already logged
+ fix the name of HardwareError
+ add test for consistency of SECoPErrors
+ catch socket.timeout in AsynTcp

Change-Id: I9df6c775cc19553b22a4d6e39591092adf7ff9a1
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/28139
Tested-by: Jenkins Automated Tests <pedersen+jenkins@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>

secop/lib/asynconn.py

@@ -167,7 +167,7 @@ class AsynTcp(AsynConn):
             uri = uri[6:]
         try:
             self.connection = tcpSocket(uri, self.defaultport, self.timeout)
-        except (ConnectionRefusedError, socket.gaierror) as e:
+        except (ConnectionRefusedError, socket.gaierror, socket.timeout) as e:
             # indicate that retrying might make sense
             raise CommunicationFailedError(str(e)) from None