Remote server: Test results stack up on multiple executions

**Citrus Version**
2.7.6

**Expected behavior**
After each remote execution only the results of the tests of the latest execution should be provided by the server under "/results". Earlier results should get cleared before e

**Actual behavior**
If there were multiple remote executions using the same remote server instance the test results of all these executions are returned by "/results".

**Test case sample**
> Please, share the test case (as small as possible) which shows the issue.

Use just any citrus test and execute them on the same remote server instance. Execute the same test multiple times. You will see that a) the test results shown on the maven log output stack up, as well as the results returned by API call /results. Unlike that the HTML report that might get generated by citrus just shows the tests of the latest execution