Ray Strode authored Aug 25, 2020 and Ray Strode committed Feb 22, 2021

KillMode=none is deprecated, so we need to stop using it.

For now, use `KillMode=mixed` and `IgnoreOnIsolate=true` instead.

In the future, we should change plymouth to be able to exit and
start again without restarting the active animation, but that's
going to require some effort.

plymouth/plymouth#123