gssd: initialize fakeseed in prepare_krb5_rfc1964_buffer

This causes a compiler warning and also means that we're stuffing
the buffer with uninitialized junk from the stack. Other places in
this code initialize "fakeseed" to 0. Do the same here.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>