trivial-httpd: Fix leak of option context
trivial-httpd: Fix leak of option context

Right now our valgrind runs also end up valgrinding the
`trivial-httpd` code, so while it doesn't matter, let's fix this leak
anyways.  We need to avoid calling `_exit()` since that won't run the
cleanup functions.

Closes: #410
Approved by: giuseppe

gatispaeglis/ostree,gatispaeglis/ostree,GNOME/ostree,gatispaeglis/ostree,GNOME/ostree,GNOME/ostree,GNOME/ostree,gatispaeglis/ostree,GNOME/ostree,gatispaeglis/ostree,gatispaeglis/ostree