title: Spring boot does not load logback-spring.xml
body: <p>I have a sample Spring Boot application that uses Logback for logging. 
  So I have <code>logback-spring.xml</code> next to the jar to configure the logging, however it does not work unless I specify it with <code>logging.config</code>, ex : <code>logging.config=logback-spring.xml</code>.</p>
  
  <p>I have looked into <a href="https://stackoverflow.com/questions/43937031/spring-boot-ignoring-logback-spring-xml">Spring Boot ignoring logback-spring.xml</a> where it suggests that it might be because there's already a <code>spring.xml</code> somewhere, but putting breakpoint on <code>org.springframework.boot.logging.AbstractLoggingSystem.initializeWithConventions(LoggingInitializationContext, LogFile)</code> shows that logFile is empty.</p>
  
  <p>Am I doing something wrong here ?</p>