INT-3300: Fix `MS` ref regression for i-c-adapter

JIRA: https://jira.springsource.org/browse/INT-3300

The change introduced by https://jira.springsource.org/browse/INT-3147
(Registration `MessageSource<?>` as bean with suffix `.source`) broke
the case where `MessageSource<?>` is a reference to existing bean.

And check to the `AbstractPollingInboundChannelAdapterParser` for type of `source` and make appropriate logic