Now actually importing into volume rather than /.

[arjen-hoogesteger]

No description provided.

[Guiorgy]

To explain what this PR does, currently vackup export produces a tar file with a vackup-volume directory where all the contents of the desired volume are inside that directory, e.g.:

$ tar -ztvf mosquitto_config.tar.gz
vackup-volume/
vackup-volume/mosquitto.conf

This PR simply skips the inclusion of this extra directory in the tar file (and handles the import accordingly):

$ tar -ztvf mosquitto_config.tar.gz
/
/mosquitto.conf

Note: Needless to say, since this changes the structure of the archive, any backups made before this change would not be correctly restored! However, since this is a simple change, you can manually update old archives, e.g.:

mkdir tmp # create a temporary directory
tar -xvzf ./mosquitto_config.tar.gz -C ./tmp # extract the archive into the temporary directory
rm ./mosquitto_config.tar.gz # delete the old archive
tar -zcvf ./mosquitto_config.tar.gz -C ./tmp/vackup-volume . # recreate the archive while skipping the vackup-volume directory
rm -rf ./tmp/ # delete the temporary directory