Use su-exec to run commands on entryponit

With su-exec, make sure the SIGTERM upon docker stop
could be received by the running program thus causing
a clean stop/exit.

Signed-off-by: Qi Zheng <qi.zheng@intel.com>

postgres/Dockerfile

@@ -17,7 +17,7 @@ RUN source /os-release && \
     mkdir /install_root \
     && swupd os-install -V ${VERSION_ID} \
     --path /install_root --statedir /swupd-state \
-    --bundles=postgresql --no-boot-update
+    --bundles=postgresql,su-exec --no-boot-update
 
 # For some Host OS configuration with redirect_dir on,
 # extra data are saved on the upper layer when the same

postgres/bootstrap.sh

@@ -51,7 +51,7 @@ if [ "$1" = 'postgres' ] && [ "$(id -u)" = '0' ]; then
 	fi
         sed -i "s|#listen_addresses.*|listen_addresses = '*'|" /usr/share/postgresql/postgresql.conf.sample
 
-	exec su postgres -s /bin/bash -c "$BASH_SOURCE $@"
+    exec su-exec postgres "$BASH_SOURCE" "$@"
 fi
 
 if [ "$1" = 'postgres' ]; then