properly handle disappearing deployment

[JensWalter]

When a deployment does no longer exists, the following error is thrown in a continuous loop:

[2021-08-16T01:16:29Z ERROR tibco_ems_operator::scaler] scale up failed: Api(ErrorResponse { status: "Failure", message: "deployments.apps \"bw-intercab-booking\" not found", reason: "NotFound", code: 404 })

If a deployment does no longer exists, it should be remove from the deployment targets.

[alexkunde]

We should test, but I believe this was fixed in this commit

[alexkunde]

not fixed

[2022-09-09T05:43:42Z ERROR tibco_ems_operator::scaler] scale down failed: ApiError: deployments.apps "rs-dlq-processor" not found: NotFound (ErrorResponse { status: "Failure", message: "deployments.apps \"rs-dlq-processor\" not found", reason: "NotFound", code: 404 })