ReconnectingCordaRPCOps is unsubscribing vault subscribers after one hour of normal operation.

`ObserverHandle.await` should block until the subscription stops or errors.

Await should probably do this

https://github.com/corda/corda/blob/7b0d177a34c96b2e34b1a302e5c8ac5e19db27da/client/rpc/src/main/kotlin/net/corda/client/rpc/internal/ReconnectingCordaRPCOps.kt#L397

https://github.com/corda/corda/blob/7b0d177a34c96b2e34b1a302e5c8ac5e19db27da/client/rpc/src/main/kotlin/net/corda/client/rpc/internal/ReconnectingCordaRPCOps.kt#L271