Test HMAC_CTX initial state and remove now unneccessary code.

The special-case in HMAC is no longer needed. Test that HMAC_CTX is initialized
with the zero key.

Change-Id: I4ee2b495047760765c7d7fdfb4ccb510723aa263
Reviewed-on: https://boringssl-review.googlesource.com/3121
Reviewed-by: Adam Langley <agl@google.com>
2 files changed