dispatcher: fix abort in case of an error (rh #1275813)

dispatcher: fix abort in case of an error (rh #1275813)

request_free() can be called on an error.

Oct 27 20:27:46 localhost.localdomain nm-dispatcher[2328]: #1 'pre-up': completed: invalid request: Missing or invalid required value path!
Oct 27 20:27:46 localhost.localdomain nm-dispatcher[2328]: **
Oct 27 20:27:46 localhost.localdomain nm-dispatcher[2328]: ERROR:nm-dispatcher.c:203:request_free: assertion failed (request->num_scripts_done == request->scripts->len): (0 == 1)

Fixes: 1999723241c49a7f2d5052d34299aad3d6e26e41

https://bugzilla.redhat.com/show_bug.cgi?id=1275813