Fix intermediate key length in hmac-md5 checksum

Fix intermediate key length in hmac-md5 checksum

pull up r25418 from trunk

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 r25418 | ghudson | 2011-10-28 11:45:03 -0400 (Fri, 28 Oct 2011) | 9 lines

 ticket: 6994
 subject: Fix intermediate key length in hmac-md5 checksum
 target_version: 1.10
 tags: pullup

 When using hmac-md5, the intermediate key length is the output of the
 hash function (128 bits), not the input key length.  Relevant if the
 input key is not an RC4 key.

ticket: 7010
version_fixed: 1.8.6
status: resolved

git-svn-id: svn://anonsvn.mit.edu/krb5/branches/krb5-1-8@25462 dc483132-0cff-0310-8789-dd5450dbe970