Fix start-slurm.sh while loop condition (#76)

ci/slurm/start-slurm.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 docker-compose up --build -d
-while [ `./register_cluster.sh | grep "sacctmgr: error" | wc -l` -ne 0 ]
+while [ `./register_cluster.sh 2>&1 | grep "sacctmgr: error" | wc -l` -ne 0 ]
   do
     echo "Waiting for SLURM cluster to become ready";
     sleep 2