[LTP] test_net.sh: Require to redefine less variables

[Petr Vorel]

Hi Alexey,

> Ah, I see, we can run them with network.sh which source test_net.sh, OK.

> Though, the left users of these functions are stress/tcp/udp/route and
> multicast stress tests...I'll post updates for the first three soon.
What exactly are you going to do?

I suppose I should wait with this until you do you push your cleanup.
> > So I'd keep all of these variables, just to calculate these with shell
> > script or C binary:
> > IPV{4,6}_NETWORK
> > {L,R}HOST_IPV{4,6}_HOST
> > IPV{4,6}_NET_REV


Kind regards,
Petr