INT-3284: Address PR's comments

JIRA: https://jira.springsource.org/browse/INT-3287

* Fix package tangle (INT-3287)
* Apply `IntegrationConfigurationInitializer` for `MBeanExporterHelper`
* Previously, there was a separate `ChannelSecurityInterceptorBeanPostProcessor`
for each `ChannelSecurityInterceptor` whereas now, there is one `ChannelSecurityInterceptorBeanPostProcessor`
that processes all interceptors