JERSEY-2164: Multi value http headers are not correctly read by the server.

 - un-ignored existing test-case + modified accordingly
 - added new test-case that actually send multiple headers for multiple values (works)

 Issue is that HTTP spec says that multiple headers can be merged into one using comma
 as separator but it doesn't say that the resulting value can be split using the
 same way.

Change-Id: Id4802481c417f8565ef95e0ea0de180c3df8d0e3
Merge "JERSEY-2164: Multi value http headers are not correctly read by the server."