radius_xlat chops embedded NULs in cisco-av-pair

[Kiril]

>  I'll take a look and see if it's fixed in later versions. It'll almost certainly work fine in 3.0.2.

I looked into the current git v3 master sources - the main thing
remais the same in vp_prints_value:

print.c, line 258
> /* xlat.c - need to copy raw value verbatim */
> else if (quote < 0) {
> return strlcpy(out, vp->vp_strvalue, outlen);

in other cases fr_print_string is used

and our company is not ready to move on freeradius v3, so we need a
solution on v2 branch