Change startall.sh script to detect WSL and translate paths for local directory creation

The persistent path used within PVC's on the host via startall.sh needs to be of the form "/run/desktop/mnt/host/c/hpccdata".
However, startall.sh fails to create the necessary stub directories for the planes inside this directory because from within WSL these paths are accessible via /mnt/c/...

Spot that startall.sh is running within WSL, and translate the paths so they can be used to create the host storage directories.