Fixes#8057
I went back and forth on the way to fix it exactly, and ended up with a
pretty simple version of a fix.
The problem was that discovery service was removing the member at the
initial phase of reset, which actually still requires KubeSpan to be up:
* leaving `etcd` (need to talk to other members)
* stopping pods (might need to talk to Kubernetes API with some CNIs)
Now leaving discovery service happens way later, when network
interactions are no longer required.
Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>