Some logs are dismissed during context creation

The default logging system is used (Logback).

For instance, the warning logged here is dismissed.
This behavior appears because at the time the warning is logged, the Logback context contains a filter that denies everything.

This issue is similar to #7758 but it's with Logback.

Here's a quick and dirty demo:

package demo;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class DemoApplication {
    private static final Logger LOGGER = LoggerFactory.getLogger(DemoApplication.class);

    @Value("${demo.value:empty}")
    private String demoValue;

    @Bean
    public CommandLineRunner commandLineRunner() {
        return new CommandLineRunner() {
            @Override
            public void run(String... args) throws Exception {
                LOGGER.warn("value = {}", demoValue);
            }
        };
    }

    public static void main(String[] args) throws Exception {
        // Valid JSON:
        // System.setProperty("SPRING_APPLICATION_JSON", "{\"demo\":{\"value\":\"demo\"}}");
        // Invalid JSON:
        System.setProperty("SPRING_APPLICATION_JSON", "{");
        SpringApplication.run(DemoApplication.class, args);
    }
}

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>demo</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.3.RELEASE</version>
    </parent>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
    </dependencies>
</project>

Start with LogbackLoggingSystem.java and SpringApplicationJsonEnvironmentPostProcessor.java at the linked locations, then run the supplied demo with invalid SPRING_APPLICATION_JSON. Trace the Logback context filter during startup and verify that the warning is no longer dismissed while context creation still completes normally.