Bug: Interaction between simulation file path and results directory

[carlaKC]

Describe the bug

If you run the simulator with two relative paths, it'll look for the simulation file in the data dir rather than the path provided and fail:

sim-cli --clock-speedup 1000 -s "lvl_acinq/simln_peacetime.json" -d "lvl_acinq/peacetime/"

[sim_cli::parsing] Simulation file 'lvl_acinq/peacetime/lvl_acinq/simln_peacetime.json' does not exist.
Error: no simulation files found in /Users/carla/Work/jam-ln/data/lvl_acinq/peacetime.

We should check whether we've got a simfile first and only fall back to the dir if it's not specified.

[alexzaitsev]

As I'm almost done with #225, I'd like to work on this next.

[alexzaitsev]

@carlaKC should it be closed?

[carlaKC]

@carlaKC should it be closed?

Yes! In future you can say "Fixes {issue number}" in your PR and then it'll auto-close the issue on merge!