Empty Watchpoint files in non-watching participants

[fsimonis]

Describe your setup

Operating system (e.g. Linux distribution and version): Yes
preCICE Version: develop (3.1.0 rc)

Describe the problem

When configuring a watchpoint in a participant, also other participants create the watchpoint log files.

This leaves empty watchpoint files around, which

• can lead to confusion of the user
• results in unnecessary files
• makes automatic data aggregation and plotting more difficult as files are not unique.
• can lead to problems when multiple participants run from the same directory as this is a filesystem race-condition. This is generally not the case though.

Step To Reproduce

1. define a watchpoint on a mesh in one participant (the elastic-tube-1d tutorial is an easy-to-run example)
2. run the case
3. find a watchpoint log file in every participant directory.

Expected behaviour

Only write log files from the participant that is being run.

Additional context

• Watchpoint/integral constructor opens the log file
• ParticipantConfiguration::finishParticipantConfiguration creates watchpoints/integrals for every configured participant.

We need #982