Fix the confparse test suite on Hurd

[Julien-Elie]

Looks like parse_include or parse_group end too early and do not keep creating nesting groups in lib/confparse.c.
Strange.

Failed Set                 Fail/Total (%) Skip Stat  Failing Tests
-------------------------- -------------- ---- ----  ------------------------
lib/confparse                 1/371    0%    2    0  247

$ ./runtests -o lib/confparse
#  left: config/link/link/link/link/link/link/link/link/link/link/link/link/link/link/link/link/link/link/link/symlink:1: file inclusions limited to 20 deep
# right: config/link/link/link/link/link/link/link/link/link/symlink:1: open of config/link/link/link/link/link/link/link/link/link/link/symlink failed
not ok 247