[3049] Do not expire session if item is a bridge

[Optijok]

When persistence true and upgrading mosquitto library from version<= 2.0.15 to version>= 2.0.16, all the clients and the bridge are expired by timeout.

Avoid expiring the bridge by checking the item context.

Bug: https://github.com/eclipse-mosquitto/mosquitto/issues/3049

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