ci: point DDS sandbox_dir to shared /data volume

DDS workers need access to the sandbox directory. Since /data is
shared across all sind nodes, redirect sandbox_dir there.

Author: dennisklein

.github/workflows/ci.yml

@@ -99,6 +99,9 @@ jobs:
             scontrol show partition
             scontrol show node
             cat /etc/slurm/slurm.conf
+            dds-user-defaults --default
+            sed -i "s|sandbox_dir=.*|sandbox_dir=/data/.DDS|" $(dds-user-defaults --config)
+            cat $(dds-user-defaults --config)
             dds-session start
             dds-submit -r slurm -n 2 --slots 4 -c /data/tests/slurm.cfg
             for i in $(seq 1 24); do