[6.1] 2f2387038 Fix gensequences for BusyBox awk

[Dridi Boukelmoune]

> But it was lost during backports. It was accidentally lost in both my
> 6.0 and Pål's 6.1 backports.

I guess both Pål and I lost it because it was also lost in the mater branch:

    $ git grep l_prefix_name -- bin/varnishtest/gensequences
    <snip>
    bin/varnishtest/gensequences:                   l_prefix_name[n] =
"teken_state_" ++npr;
    <snip>

The change was overwritten in this commit:

commit f2abaf8698a34a44d8a80d80756b0f843560e31d
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Mon Sep 24 07:31:46 2018 +0000

    Update Teken from FreeBSD source tree

phk, maybe you should upstream the fix to avoid running into the same
situation with the next teken update?

Dridi