BUG: force write into a separated file instead of overwriting

Summary

force write into a separated file named force_0.dat instead of overwriting the existing file when restarting from a time step that has started previously. Same behavior found when writing moment. This is quite annoying when the first time of running failed (due to CFL being too big or something), then restarted.

Steps to reproduce

1. Start a transient simulation with force writer.
2. You can stop the simulation once the force writer writes something in postProcessing/0/force.dat
3. Restart from the same time step.
4. You will see a force.dat and force_0.dat in postProcessing/0/
5. This behavior can be replicated not necessarily at 0 time step.

Example case

What is the current bug behaviour?

What is the expected correct behavior?

Relevant logs and/or images

Environment information

• OpenFOAM version : v2012
• Operating system : centos (i dont think it matters)
• Hardware info : VM
• Compiler : gcc

Possible fixes