XD-1861 Fix XD config logger

- Spring Boot 1.1.1 has the following change:
https://github.com/spring-projects/spring-boot/commit/b75578d99c8d435e1f8bf18d0dbb3a2ddf56fdc4
where, an external property source precedence would get re-ordered after the application configuration properties.
This change affects Spring XD config initializer which expects an external "zk-properties" property source
always preceding over the application configuration properties.

 - Fix XdConfigLoggingInitializer to explicitly check for `zk-properties` property source and obtain the
zk connection properties (for standalone/embedded case) before logging the appropriate value.
 - Log transport option for admin server