Improve test coverage around NewSessionTicket message.

Test both when the peer doesn't support session tickets and when the server
promises a NewSessionTicket message but doesn't deliver.

Change-Id: I48f338094002beac2e6b80e41851c72822b3b9d5
Reviewed-on: https://boringssl-review.googlesource.com/1300
Reviewed-by: Adam Langley <agl@google.com>