Fix failing data.sh in OWSM

[cifkao]

What?

Theegs2/owsm_v1/s2t1/local/data.sh script is exiting for every dataset: ./local/prepare_${dataset}.sh || echo "preparing ${dataset} failed" gets executed first and always evaluates to true, so exit 1 will always get executed. I grouped the echo and the exit to fix this.

@pyf98

[sw005320]

Thanks!