[2.3.x] + fix issue #1644
https://java.net/jira/browse/GRIZZLY-1644

"CTS test getContentTypeNull2Test fails"

+ unit test added
[2.3.x] + minor logging cleanup
[2.3.x] + fix issue #1645
https://java.net/jira/browse/GRIZZLY-1645

"IdleTimeoutFilter racing"