Comment 15 for bug 1815101

The commits bellow implement support to "keep configuration":

commit 1e498853a39b46155cb89b5c9e74ecb27aaba3ed
Author: Yu Watanabe <email address hidden>
Date: Mon Jun 3 01:21:13 2019

    test-network: add tests for KeepConfiguration=

commit c98d78d32abba6aadbe89eece7acf0742f59047c
Author: Yu Watanabe <email address hidden>
Date: Mon Jun 3 03:37:25 2019

    man: add documentation about KeepConfiguration

commit db51778f85cb076e9ed1fe7f7e29cc740365c245
Author: Yu Watanabe <email address hidden>
Date: Mon Jun 3 00:33:13 2019

    network: make KeepConfiguration=static drop DHCP addresses and routes

    Also, KeepConfiguration=dhcp drops static foreign addresses and routes.

commit 95355a281c06c5970b7355c38b066910c3be4958
Author: Yu Watanabe <email address hidden>
Date: Mon Jun 3 14:05:26 2019

    network: add KeepConfiguration=dhcp-on-stop

    The option prevents to drop lease address on stop.
    By setting this, we can safely restart networkd.

commit 7da377ef16a2112a673247b39041a180b07e973a
Author: Susant Sahani <email address hidden>
Date: Mon Jun 3 00:31:13 2019

    networkd: add support to keep configuration

for systemd-networkd.

IMO, we should rely in setting the keep configuration flag for the interfaes to be managed by 3rd part software (adding/removing aliases for virtual networks, VRRP interfaces, etc).