Rework and simplify gssapi_vm2gssbuf() so that we don't accidentally pass a bogus address to free().
Rework and simplify gssapi_vm2gssbuf() so that we don't accidentally
pass a bogus address to free().

MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame