Revert "Drop retransmits in DTLS tests."

This reverts commit c67a3ae6babb8accceb6854ec5167cd8b1d19e2f. With a
deterministic clock, we can now go back to being strict about retransmits. Our
tests will now require that the shim only retransmit when we expect it to.

Change-Id: Iab1deb9665dcd294790c8253d920089e83a9140c
Reviewed-on: https://boringssl-review.googlesource.com/3211
Reviewed-by: Adam Langley <agl@google.com>
2 files changed