s4:lib/http: rewrite http_send_auth_request_*() using gensec_update_send/recv

s4:lib/http: rewrite http_send_auth_request_*() using gensec_update_send/recv

The new logic makes it much clearer that we have a loop of

gensec_update_send()
gensec_update_recv()
http_send_request_send()
http_send_request_recv()
http_read_response_send()
http_read_response_recv()

Until the local gensec and the server are ready.

I've tested this against Windows 2008R2 like this:

bin/smbtorture \
  -W BLA --realm=BLA.BASE \
  -s /dev/null -Uadministrator%A1b2C3d4 \
  ncacn_http:w2k8r2-219[593,RpcProxy=w2k8r2-219.bla.base,HttpUseTls=false,HttpAuthOption=basic] \
  rpc.epmapper.epmapper.Lookup_simple \

and:

bin/smbtorture \
  -W BLA --realm=BLA.BASE \
  -s /dev/null -Uadministrator%A1b2C3d4 \
  ncacn_http:w2k8r2-219[593,RpcProxy=w2k8r2-219.bla.base,HttpUseTls=false,HttpAuthOption=ntlm] \
  rpc.epmapper.epmapper.Lookup_simple \

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>