squash w/ startup/shutdown. Add dedicated upgrade python script for u…

…pgrading the server.

scripts/irods/upgrade_configuration.py

@@ -290,11 +290,13 @@ def update_base(base, updates):
 
     new_server_config = update_base(base, server_config)
 
-    # Prompt the admin for the host which uniquely identifies this server.
-    new_server_config['host'] = lib.default_prompt(
-        'iRODS server FQDN, hostname, or IP (256 characters max)',
-        default=lib.get_hostname(),
-        input_filter=lib.character_count_filter(minimum=1, maximum=256, field='iRODS server host'))
+    # Prompt the admin for the host which uniquely identifies this server, but only
+    # if the property doesn't exist in the new server_config.json configuration.
+    if 'host' not in new_server_config:
+        new_server_config['host'] = lib.default_prompt(
+            'iRODS server FQDN, hostname, or IP (256 characters max)',
+            default=lib.get_hostname(),
+            input_filter=lib.character_count_filter(minimum=1, maximum=256, field='iRODS server host'))
 
     # Remove keys that are no longer needed by the server.
     # Keys listed here are ones that used to be recognized by the server.