Remove the weak key checks from the builtin rc4 enc provider. There

Remove the weak key checks from the builtin rc4 enc provider.  There
is no standards support for avoiding RC4 weak keys, so rejecting them
causes periodic failures.  Heimdal and Microsoft do not check for weak
keys.  Attacks based on these weak keys are probably thwarted by the
use of a confounder, and even if not, the reduction in work factor is
not terribly significant for 128-bit keys.

ticket: 6886
target_version: 1.9.1
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@24750 dc483132-0cff-0310-8789-dd5450dbe970