Adjust a couple of migrations

I had forgot the include logic to not run some migrations if the changes
have already taken place. This skip is just the "naive" approach instead
of doing a complete validation that the previous fields have migrated.

broker/config_migrations/v0_6_0.py

@@ -37,7 +37,10 @@ def remove_test_nick(config_dict):
 
 
 def move_ssh_settings(config_dict):
-    """Move SSH settings from the top leve into its own chunk."""
+    """Move SSH settings from the top level into its own chunk."""
+    # Check if the migration has already been performed
+    if "ssh" in config_dict:
+        return config_dict
     logger.debug("Moving SSH settings into their own section.")
     ssh_settings = {
         "backend": config_dict.pop("ssh_backend", "ssh2-python312"),
@@ -57,7 +60,7 @@ def move_ssh_settings(config_dict):
 def add_thread_limit(config_dict):
     """Add a thread limit to the config."""
     logger.debug("Adding a thread limit to the config.")
-    config_dict["thread_limit"] = None
+    config_dict["thread_limit"] = config_dict.get("thread_limit")
     return config_dict
 
 
@@ -73,6 +76,8 @@ def add_inventory_fields(config_dict):
         Action: $action  # some special field values are possible, check the wiki
         OS: os_distribution os_distribution_version  # you can combine multiple values with a space between
     """
+    if "inventory_fields" in config_dict:
+        return config_dict
     logger.debug("Adding inventory fields to the config.")
     config_dict["inventory_fields"] = {
         "Host": "hostname",

broker/helpers.py

@@ -328,7 +328,7 @@ def _resolve_inv_field(field, host_dict, **extras):
     if "|" in field:
         resolved = [_resolve_inv_field(f.strip(), host_dict, **extras) for f in field.split("|")]
         for val in resolved:
-            if val:
+            if val and val != "Unknown":
                 return val
         return "Unknown"
     # Users can combine multiple values in a single field, so evaluate each