Reduce the WARNING to a DEBUG when SNI support is enabled.

This is because a) during SNI such is normal and b) regardless 
when overlap is detected there will always be a warning:

    [warn] Init: Name-based SSL virtual hosts only work for clients 
       with TLS server name indication support (RFC 4366)

at the end of the cycle.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@620505 13f79535-47bb-0310-9956-ffa450edef68