iotests: define group in each iotest

iotests: define group in each iotest

We are going to drop group file. Define group in tests as a preparatory
step.

The patch is generated by

    cd tests/qemu-iotests

    grep '^[0-9]\{3\} ' group | while read line; do
        file=$(awk '{print $1}' <<< "$line");
        groups=$(sed -e 's/^... //' <<< "$line");
        awk "NR==2{print \"# group: $groups\"}1" $file > tmp;
        cat tmp > $file;
    done

Signed-off-by: Vladimir Sementsov-Ogievskiy <[email protected]>
Reviewed-by: Eric Blake <[email protected]>
Message-Id: <20210116134424[email protected]>
Signed-off-by: Eric Blake <[email protected]>