clients: Free output->make/model in output_destroy

== 8 bytes in 1 blocks are definitely lost in loss record 4 of 71
==    at 0x48450F8: malloc (vg_replace_malloc.c:309)
==    by 0x500213F: strdup (strdup.c:42)
==    by 0x40A57F: display_handle_geometry (in weston-desktop-shell)
==    by 0x4864D27: ffi_call_SYSV (in libffi.so.6.0.4)
==    by 0x4865697: ffi_call (in libffi.so.6.0.4)
==    by 0x4880E07: wl_closure_invoke (connection.c:935)
==    by 0x487DD73: dispatch_event.isra.5 (wayland-client.c:1310)
==    by 0x487EF87: dispatch_queue (wayland-client.c:1456)
==    by 0x487EF87: wl_display_dispatch_queue_pending (wayland-client.c:1698)
==    by 0x4104E3: handle_display_data (in weston-desktop-shell)
==    by 0x40FE8F: display_run (in weston-desktop-shell)
==    by 0x405AB3: main (in weston-desktop-shell)

Signed-off-by: Lujin Wang <luwang@nvidia.com>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>