Fix "No context found:" warnings from Mapper.addWrappers() -> findContextVersion() during context startup.
If context has not been started yet, its "AFTER_START" lifecycle event will come later.

A typical stacktrace:
SEVERE [main] org.apache.catalina.mapper.Mapper.findContextVersion No context found: 
	at org.apache.catalina.mapper.Mapper.findContextVersion(Mapper.java:372)
	at org.apache.catalina.mapper.Mapper.addWrappers(Mapper.java:401)
	at org.apache.catalina.mapper.MapperListener.registerWrapper(MapperListener.java:430)
	at org.apache.catalina.mapper.MapperListener.containerEvent(MapperListener.java:154)
	at org.apache.catalina.core.ContainerBase.fireContainerEvent(ContainerBase.java:1186)
	at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:732)
	at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:700)
	at org.apache.catalina.core.StandardContext.addChild(StandardContext.java:2738)
	at org.apache.catalina.startup.ContextConfig.configureContext(ContextConfig.java:1364)
	at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1177)
	at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:767)
	at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:302)
	at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
	at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
	at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5083)

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1610244 13f79535-47bb-0310-9956-ffa450edef68