MINOR: try-finally around super call in http.py (#12924)

Reviewers: Daniel Gospodinow <danielgospodinow@gmail.com>, Ian McDonald <imcdonald@confluent.io>, Manikumar Reddy <manikumar.reddy@gmail.com>

tests/kafkatest/services/monitor/http.py

@@ -94,8 +94,9 @@ class HttpMetricsCollector(object):
         super(HttpMetricsCollector, self).start_node(node)
 
     def stop(self):
+        try:
             super(HttpMetricsCollector, self).stop()
-
+        finally:
             if self._http_metrics_thread:
                 self.logger.debug("Shutting down metrics httpd")
                 self._httpd.shutdown()