fix(test/virtio-mem): ensure RuntimeError is raised with matching reason

We should match the exact reason for the RuntimeError to ensure we're
failing for what we're expecting.

Signed-off-by: Riccardo Mancini <[email protected]>

Author: Manciukic

tests/integration_tests/functional/test_api.py

@@ -1006,7 +1006,7 @@ def test_api_memory_hotplug(uvm_plain):
     test_microvm.start()
 
     # Put API should be rejected after boot
-    with pytest.raises(RuntimeError):
+    with pytest.raises(RuntimeError, match=NOT_SUPPORTED_AFTER_START):
         test_microvm.api.memory_hotplug.put(total_size_mib=1024)
 
     # Get API should work after boot