Fix formatting issue in docker_shell.sh

- docker_shell.sh should now be able to connect to running container instance.

Author: ntdkhiem

docker_shell.sh

@@ -1,6 +1,6 @@
 CURR_DIR="${PWD##*/}"
 
-RUNNING_ID="docker ps --format '{{.ID}}' -f 'ancestor=${CURR_DIR}_rails'"
+RUNNING_ID="docker ps --format '{{.ID}}' -f 'ancestor=${CURR_DIR}-rails'"
 if [[ "$RUNNING_ID" == "" ]]; then
     echo Running new container instance
     ./docker/docker_run.sh ${@:-/bin/bash}