PlugAlarm may be handled incorrectly in case ReadRequest is pending while alarm is handled

A PlugAlarm requires specific handling of IO Controller. After application acknowledges the Alarm, the Parameters have to be sent to submodule (via WriteRecord) followed by a ParameterEnd request. Afterwards the alarm is fully confirmed by sending the high level Alarm Acknowledge.

Instead of this sequence, it may happen that the IO Controller directly sends the high level Alarm Acknowledge and completely skips sending parameters and ParameterEnd.

The isse occurs in the following situation:

• Alarm is received and indicated to application for handling
• Application sends out any kind of ReadRequest to the IO Device which issued the Alarm. The submodule which is read is irrelevant, the ReadRequest itself is problematic.
• While the ReadRequest is pending on the network (not responded by IO Device), the application acknowledged the alarm

Instead of waiting for the ReadConfirmation first and sending the parameters afterwards, the IO Controller internaly detects that parameters can not be written and completely skips this step.