daemon: No longer needs its own copy of gnulib.

Since the daemon has long since used the same build system as the rest
of libguestfs, it no longer needs its own gnulib.

This arcane bit of code was left over from
commit e05ddc70f1fa6d1e8253d69c5d17e69bfad2be90 (added 2009-08-03 !)