fix: Only prompt to delete home if --rm-home is passed

[AdamIsrael]

Only prompt the user to delete their mounted home directory (if it differs from $HOME) if they pass the --rm-home flag.

$ distrobox-rm -f acme
acme

$ distrobox-rm -f --rm-home acme
Do you want to remove custom home of container acme (/var/home/stone/Clients/ACME)? [y/N]: y
acme
Successfully removed /var/home/stone/Clients/ACME

This is a suggested solution to the pending discussion in issue #894 and resolves the issue raised in #895.

[89luca89]

Thanks! This is indeed very important, thanks a lot for the contribution! 😄