test: box/errinj -- sort errors

Every new error introduced into error engine cause massive update in
test even if only one key is introduced.

To minimize diff output better print them in sorted order.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Reviewed-by: Alexander Turenko <alexander.turenko@tarantool.org>
(cherry picked from commit 95b9a48d)