fetcher/curl: Fix invalid memory access in finalize()
fetcher/curl: Fix invalid memory access in finalize()

Reorder cleanup functions so that curl_multi_cleanup() runs before
self->sockets is destroyed. This avoids an assert and invalid memory
access in sock_cb where self->sockets is dereferenced during
curl_multi_cleanup().

Closes: https://github.com/ostreedev/ostree/issues/1331

Closes: #1332
Approved by: cgwalters

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