Fix issue with tests + some cleaning.

tests/conftest.py

@@ -62,12 +62,12 @@ async def app() -> FastAPI:
 
 
 @pytest.fixture(scope="class")
-def db_engine():
+async def db_engine():
 
     db_url = os.getenv("GNS3_TEST_DATABASE_URI", "sqlite+aiosqlite:///:memory:")  # "sqlite:///./sql_test_app.db"
     engine = create_async_engine(db_url, connect_args={"check_same_thread": False}, future=True)
     yield engine
-    engine.sync_engine.dispose()
+    #await engine.sync_engine.dispose()
 
 
 @pytest.fixture(scope="class")