send_as_req re-encodes the request

send_as_req re-encodes the request

krb5_get_init_creds calls encode_krb5_as_req to produce an encoding
for the preauth plugins, then passes the unencoded request structure
into the static function send_as_req.  That function re-encodes the
request.  This is an unnecessary call to the encoder.  In addition,
for the FAST project, it is desirable to encapsulate the unencoded
outer request so that krb5_get_init_creds does not need it.

* send_as_req is modified to take an encoded request and realm
* Remove unused logic to fill in request nonce from send_as_req

ticket: 6401

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@22067 dc483132-0cff-0310-8789-dd5450dbe970