kolla-images.py: Add image map exception for neutron_eswitchd

This was not caught because neutron-mlnx-agent is not in the list of
supported images in pulp.yml.

Author: markgoddard

tools/kolla-images.py

@@ -52,6 +52,7 @@
         "mariabackup",
     ],
     "neutron-mlnx-agent": [
+        "neutron_eswitchd",
         "neutron_mlnx_agent",
     ],
     "neutron-metadata-agent": [