Close connection after use in LiquibaseEndpoint

Update LiquibaseEndpoint so that connections are closed and returned to
the pool after use.

Fixes gh-6118

spring-boot-actuator/src/main/java/org/springframework/boot/actuate/endpoint/LiquibaseEndpoint.java

@@ -54,9 +54,14 @@ public class LiquibaseEndpoint extends AbstractEndpoint<List<Map<String, ?>>> {
 			DatabaseFactory factory = DatabaseFactory.getInstance();
 			DataSource dataSource = this.liquibase.getDataSource();
 			JdbcConnection connection = new JdbcConnection(dataSource.getConnection());
+			try {
 				Database database = factory.findCorrectDatabaseImplementation(connection);
 				return service.queryDatabaseChangeLogTable(database);
 			}
+			finally {
+				connection.close();
+			}
+		}
 		catch (Exception ex) {
 			throw new IllegalStateException("Unable to get Liquibase changelog", ex);
 		}