Remove the existing md5_test and sha1_test. They now are all covered by
digest_test. For good measure, test the one-shot functions too.
Change-Id: I8e144cc563fb8817144e26cbd2e10c15642464ba
Reviewed-on: https://boringssl-review.googlesource.com/2211
Reviewed-by: Adam Langley <agl@google.com>
