coroparse: Free kv_item key and value on failure

If strdup of kv_item key or value failed only kv_item itself was freed.
Free also key and value (kv_item is zeroed so free of NULL variable is
safe).

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>