[Swan] using esp=null, auth=null for testing/devel..

[Sowmini Varadhan]

I'd like to set up both esp and auth to NULL to test some kernel
code (for perf, so want to eliminate the cost of crypto).

with older swan packages, I was able to use the syntax "esp=null-null"
for this, but with libreswan-3.15-7.3.0.1.el6.x86_64, the only syntax
that is accepted in my tunnel .conf file is "esp=null", and this 
leaves me with the following in the output of "ip x s"
        :
        proto esp spi 0x53b065c6 reqid 16389 mode transport
        replay-window 32 
        auth-trunc hmac(md5) 0xd374a491490abf161152bef3108816c8 96
        enc ecb(cipher_null) 
        :

is there some way I can set the auth-trunc to null too? 

--Sowmini