docker test: Re-create automation user if it exists already

To avoid errors when reusing the containerized site, the automation
user is re-created if it exists already.

Change-Id: I70217e59b95478d130fb154dc121751206989706

tests/testlib/docker.py

@@ -379,6 +379,10 @@ def __exit__(self, exc_type, exc_value, traceback):
         self._teardown()
 
     def _create_automation_user(self) -> None:
+        if self.openapi.users.get(self.api_user):
+            logger.info("Dropping existing test-user: '%s'", self.api_user)
+            self.openapi.users.delete(self.api_user)
+        logger.info("Creating automation user: '%s'.", self.api_user)
         self.openapi.users.create(
             username=self.api_user,
             fullname="Automation user for tests",