[2.3.x] "minor updates"
[2.3.x] + fix issue #1545
https://java.net/jira/browse/GRIZZLY-1545
"SpdyHandlerFilter doesn't process FLUSH event properly"
[2.3.x] + minor update
[2.3.x] + fix issue
https://java.net/jira/browse/GLASSFISH-20694
"Glassfish 4.0 and jk Unable to populate SSL attributes"
Incremental changes for https://java.net/jira/browse/GRIZZLY-1546 (Ref GRIZZLY-1345. Generalize the graceful shutdown to be a feature of the core transport vs specific to http-server).
  - In addition to the feature changes, refactored common loggic from {TCP,UDP}NIOTransport into NIOTransport.  Doing so
    removed duplicate logic in both concrete transport classes as well as removing duplicate test code.