Try all history keys to decrypt password history

Try all history keys to decrypt password history

A database created prior to 1.3 will have multiple password history
keys, and kadmin prior to 1.8 won't necessarily choose the first one.
So if there are multiple keys, we have to try them all.  If none of
the keys can decrypt a password history entry, don't fail the password
change operation; it's not worth it without positive evidence of
password reuse.

ticket: 7099

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@25819 dc483132-0cff-0310-8789-dd5450dbe970