Clean up dispatch lookaside code slightly

Clean up dispatch lookaside code slightly

Always log when we get a lookaside cache hit, eliminating a confusing
conditional.  This is a slight behavior change because we never used
to log a lookaside cache hit when we can't deliver the response via
UDP, but that was never really deliberate or important--we log all
sorts of stuff about responses which might turn out to be too big.

Also eliminate a signed/unsigned comparison warning in
finish_dispatch.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@25661 dc483132-0cff-0310-8789-dd5450dbe970