Fix: Hanging transaction in whois plugin configuration (re)load.

* This makes the ORM query handling to be in line with SQLAlchemy's design and expectations.

(Redmine issue: #4251)

lib/mentat/services/whois.py

@@ -256,7 +256,6 @@ class SqldbWhoisModule(WhoisModule):
 
         # Load network records from SQL database.
         records = storage.session.query(mentat.datatype.sqldb.NetworkModel).all()
-        storage.session.commit()
 
         # Generate list of internal network record objects.
         networks = []
@@ -272,7 +271,7 @@ class SqldbWhoisModule(WhoisModule):
             networks.append(netw)
 
         # Rollback any changes, we are not supposed to change anything.
-        #storage.session.rollback()
+        storage.session.rollback()
 
         # Let the parent implementation take care of loading internal lookup table.
         return super().setup(networks)