Fix/disk resize on wsl

[thabich]

Without the fix Vagrant will first fail due to an added ./ in front of the file names.

This command adds a ./ in front of destination (WSL only).
destination = File.join(File.dirname(source), File.basename(source, ".*")) + ".vdi"

I have tried in the least invasive way to avoid this for WSL, by simply removing it again.

At the point when a backup is being performed, there are larger path issues. The simple mv command, doesn't work on WSL, so I am using:
machine.provider.driver.clone_disk(defined_disk[:location], backup_disk_location, "VMDK")
to create a copy of the VMDK file. As this copy will receive a new UUID in case it's require, the UUID will be restored and the file will be moved back to it's old position. At this point we've reached the same situation as for non WSL setups.

The main approach is to fix the issue for WSL, while leaving the rest of the procedure untouched.

[hashicorp-cla-app]

All committers have signed the CLA.

[thabich]

@taru-garg-hashicorp sorry to bother, is there still active development on Vagrant? Is it worth to create another bug fix for another broken WSL feature? (it seems that it's not possible to use cloud-init, due to path issues with the iso build). Is there any chance to get my PR merged?