Ensure all entrypoints exec their final command

This avoids keeping around a useless shell process, and allows killing
the "init" process to always DTRT

apps/swh-indexer/entrypoint.sh

@@ -17,7 +17,7 @@ fi
 
 # start the replayer
 echo "Starting indexer journal client..."
-swh \
+exec swh \
   --log-level $LOGLEVEL \
   --log-level azure.core.pipeline.policies.http_logging_policy:WARNING \
   indexer \

apps/swh-storage-replayer/entrypoint.sh

@@ -12,4 +12,4 @@ fi
 
 # start the replayer
 echo "Starting the replayer..."
-swh storage replay
+exec swh storage replay