If teaming is set up via NetworkManager we don't want systemd to take
down the userspace teamd process when NetworkManager quits. `KillMode=process`
will allow it to leave those processes behind.
This is fallout from the change to run NetworkManager via systemd (
c17c5b7).
With `KillMode=process` we get something like:
```
sh-5.1# journalctl -u nm-run -o cat | tail
<info> [
1618411262.7030] quitting now that startup is complete
<info> [
1618411262.7030] device (team0): carrier: link connected
<info> [
1618411262.7033] device (team0): team port ens2 was released
<info> [
1618411262.7033] device (team0): team port ens3 was released
<info> [
1618411262.7033] manager: NetworkManager state is now CONNECTED_SITE
<info> [
1618411262.7034] exiting (success)
nm-run.service: Deactivated successfully.
nm-run.service: Unit process 476 (teamd) remains running after unit stopped.
Finished nm-run.service.
```
#run the script and wait before it finishes
Type=oneshot
ExecStart=/usr/sbin/NetworkManager --configure-and-quit=initrd --no-daemon
+#don't kill forked off processes (for example: teamd for teaming)
+KillMode=process
[Install]
WantedBy=initrd.target