Revert "storage: For FS pool check for properly formatted target volume"

Revert "storage: For FS pool check for properly formatted target volume"

The check does not work properly (crashes) with netfs filesystems and
also checking that a device is not empty when attempting to mount a
filesystem is not very usefull since the mount will fail anyways.

As the code would improve only a very minor corner case I don't really
see a reason to have this code at all.

This code would also fail if libvirt is compiled without support for
blkid and without parted.

This reverts commit a11fd69735e6951cda9bf256d8e423696a441aa4.