dhcp: if first ntp invocation fails, set time manually and retry

[rpardini]

• 🍃 some machines have no RTC at all, or an RTC with a failed battery
• 🌴 in certain situations, ntpd fails with "Alarm Clock" when trying to do too-big a jump
• 🌵 in this case, set system time to the date of the dhcpd binary and retry
• 🌳 yet-another-case where systemd would have saved us from pain

[mergify]

Merge Queue Status

✅ The pull request has been merged at ffb856b

This pull request spent 6 minutes 27 seconds in the queue, including 6 minutes 8 seconds running CI.
The checks were run on draft #317.

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• #changes-requested-reviews-by=0
  • dhcp: if first ntp invocation fails, set time manually and retry #304
• #review-requested=0
  • dhcp: if first ntp invocation fails, set time manually and retry #304
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  • dhcp: if first ntp invocation fails, set time manually and retry #304
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    • dhcp: if first ntp invocation fails, set time manually and retry #304
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