Netdata never ending restarts after a reboot

[julsemaan]

Saw 2 cases of netdata being in an endless restart loop that seemed to be triggered by systemd because of a timeout while starting.

@fdurand added a "sleep 30" in the startup for netdata to wait until other services are ready because the plugins didn't have a retry logic built-in.

We should use autodetection retry for all the plugins if possible and remove the systemd spaghetti and "sleep 30" from the netdata unit since it will be able to detect services by retrying its checks.