Introduce retry mechanism when starting embedded servlet containers in unit tests

In the unit tests which uses the embedded servlet container an intermittent issue can occur without this change, because those tests start the container on a specific port, which is available at the start of the unit tests. However, in some corner cases, it can happen that the port is being available at the start of the test, but some process occupies that port meanwhile, leading to a `java.net.BindException: Address already in use` exception during the unit test's execution.

The goal of this ticket is resolve this by introducing a retry mechanism when starting the embedded servlet container.