Fix sample tests to avoid metrics/mongo startup failures (#3122)

Signed-off-by: keyu lu <minizhiren@outlook.com>

Author: minizhiren

spring-cloud-config-sample/src/test/resources/application.properties

@@ -0,0 +1,6 @@
+# Micrometer's global registry can introduce nondeterministic state between tests.
+# These sample tests do not verify metrics, so we disable global metric/tracing registration.
+management.metrics.use-global-registry=false
+management.metrics.export.simple.enabled=false
+management.observations.enabled=false
+management.tracing.enabled=false