msdk: ignore MFX_ERR_UNDEFINED_BEHAVIOR when loading a plugin
An issue can be seen when using msdkh265enc with bitrate change in playing state. The root cause is the corresponding plugin is loaded again.
Returning MFX_ERR_UNDEFINED_BEHAVIOR from MSDK just means the plugin has been loaded, so we may ignore this error when doing configuation again in the sub class, otherwise the pipeline will be interrupted