Compatibility tests were updated with fixed v2.25 version.

A bug with unabling to terminate `dnet_ioserv` (v2.25) with **SIGTERM**, when
v2.26-nodes were trying to connect to v2.25-nodes was fixed in v2.25.6.13.
Merge pull request #81 from kis8ya/features/compatibility-tests-update

Compatibility tests were updated with fixed v2.25 version.