mkfs: make less noisy

mkfs: make less noisy

Easiest and cleanest would be to pass the -q quiet parameter, but
that drops also possible relevant information when rescuing such a
filesystem (super block backup positions, UUID, ...)

Will let thorugh something like:

> Creating filesystem with 262144 4k blocks and 65536 inodes
> Filesystem UUID: 3a6f3548-baf6-45fa-93d2-b61212668d23
> Superblock backups stored on blocks:
> 	32768, 98304, 163840, 229376

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>