LU-2384 kerberos: Support for MIT-kerberos >=1.8.X is broken

LU-2384 kerberos: Support for MIT-kerberos >=1.8.X is broken

Since version 1.8.X the function signature for deriving
cryptographic keys of the MIT-kerberos library:
krb5_derive_key(const struct krb5_enc_provider *enc,
                const krb5_keyblock *inkey,
                krb5_keyblock *outkey,
                const krb5_data *in_constant)
is changed in:
krb5int_derive_key(const struct krb5_enc_provider *enc,
                   krb5_key inkey, krb5_key *outkey,
                   const krb5_data *in_constant)
The kerberos support for lustre thus is not working anymore
with current linux distributions supporting MIT-kerberos
library >= 1.8.X.

Signed-off-by: Andrew Korty <ajk@iu.edu>
Change-Id: I35e85a15e7fd846df6d63d430d7ac98ec53d7c56
Reviewed-on: http://review.whamcloud.com/4672
Tested-by: Hudson
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>