fstests: mkfs the scratch device if we have missing profiles

fstests: mkfs the scratch device if we have missing profiles

I have a btrfs config where I specifically exclude raid56 testing, and
this resulted in btrfs/011 failing with an inconsistent file system.
This happens because the last test we run does a btrfs device replace of
the $SCRATCH_DEV, leaving it with no valid file system.  We then skip
the remaining profiles and exit, but then we go to check the device on
$SCRATCH_DEV and it fails because there is no file system.

Fix this to re-make the scratch device if we skip any of the raid
profiles.  This only happens in the case of some idiot user configuring
their testing in a special way, in normal runs of this test we'll never
re-make the fs.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>