test: RED - Updated keys must survive, if HAProxy reloads

test: RED - Updated keys must survive, if HAProxy reloads

* The Handover-IT hast to signal HAProxy to reload, after a new backend was
  started for the first time.
* Otherwise, HAProxy is not able to detect newly started backend-instances,
  because with docker, the name of a backend cannot be resolved, before it
  is started.
* This test formulates the expectation, that dynamically added changes,
  that were applyed with the help of the Data Plane API, persist a reload.
* *The test fails*, because HAProxy restores all maps from disk, if it
  reloads, but the dynamically made changes are never synced back to disk.