Fix connection leak in check_database_connection

Only check session.connection().invalidated when there's an existing
transaction. This avoids checking out a new connection from the pool
that would never be returned, causing "too many clients" errors during
integration tests.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: mvdbeek

lib/galaxy/model/base.py

@@ -61,7 +61,7 @@ def check_database_connection(session):
     if isinstance(session, scoped_session):
         session = session()
     trans = session.get_transaction()
-    if (trans and not trans.is_active) or session.connection().invalidated:
+    if trans and (not trans.is_active or session.connection().invalidated):
         session.rollback()
         log.error("Database transaction rolled back due to inactive session transaction or invalid connection state.")