[COMMON] Fix $BASH_SOURCE and pushd/popd bashisms

pointed out by checkbashisms.

Issue-ID: OOM-2643
Signed-off-by: Guillaume Lambert <guillaume.lambert@orange.com>
Change-Id: Ic9c4edc0fc6bd94a95bcb85d84379e868fb09930
diff --git a/kubernetes/common/cassandra/resources/config/docker-entrypoint.sh b/kubernetes/common/cassandra/resources/config/docker-entrypoint.sh
index 5b65222..64c7daa 100644
--- a/kubernetes/common/cassandra/resources/config/docker-entrypoint.sh
+++ b/kubernetes/common/cassandra/resources/config/docker-entrypoint.sh
@@ -11,7 +11,7 @@
 if [ "$1" = 'cassandra' -a "$(id -u)" = '0' ]; then
         find /var/lib/cassandra /var/log/cassandra "$CASSANDRA_CONFIG" \
                 \! -user cassandra -exec chown cassandra '{}' +
-        exec gosu cassandra "$BASH_SOURCE" "$@"
+        exec gosu cassandra "$0" "$@"
 fi
 
 _ip_address() {