HDDS-14887. BASH_SOURCE0: unbound variable (apache#9975)

Author: Russole

hadoop-ozone/dist/src/main/compose/ozone-balancer/test-ec.sh

@@ -19,7 +19,7 @@
 
 set -u -o pipefail
 
-COMPOSE_DIR="$( cd "$( dirname "${BASH_SOURCE0}" )" >/dev/null 2>&1 && pwd )"
+COMPOSE_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
 export COMPOSE_DIR
 export OM_SERVICE_ID="om"
 export OM=om1