Use cached blacklist on startup to improve startup times

Expected Behaviour:

Startup should be fast. Is there a way to skip downloading the blacklist updates on startup, use the existing ones and then update in the background?

Actual Behaviour:

Startup is slow. Downloading the blacklist updates can take a long time, or fail sometimes. The startup processes waits for these to finish.

Debug Token:

https://tricorder.pi-hole.net/lnl4q7johm

Pi-hole doesn't download block list updates on startup, it only loads the block lists when gravity is rebuilt. Under normal operation, gravity is updated once weekly on Sunday morning between 3 am and 5 am your local time.

The startup logs show it attempting to download and not starting until after:

::: Docker start setup complete
[i] Pi-hole blocking is enabled
[i] Neutrino emissions detected...
[✓] Pulling blocklist source list into range

[i] Target: mirror1.malwaredomains.com (justdomains)

[✗] Status: Connection Refused
[✗] List download failed: using previously cached list

[i] Target: sysctl.org (hosts)
[✗] Status: Connection Refused
[✗] List download failed: using previously cached list

[i] Target: s3.amazonaws.com (simple_tracking.txt)
[✗] Status: Connection Refused
[✗] List download failed: using previously cached list

[i] Target: s3.amazonaws.com (simple_ad.txt)
[✗] Status: Connection Refused
[✗] List download failed: using previously cached list

[i] Target: raw.githubusercontent.com (hosts)
[✗] Status: Connection Refused
[✗] List download failed: using previously cached list

[✓] Consolidating blocklists
[✓] Extracting domains from blocklists
[i] Number of domains being pulled in by gravity: 127955
[✓] Removing duplicate domains
[i] Number of unique domains trapped in the Event Horizon: 117007
[i] Number of whitelisted domains: 0
[i] Number of blacklisted domains: 0
[i] Number of regex filters: 3
[✓] Parsing domains into hosts format
[✓] Cleaning up stray matter

[✓] DNS service is running
[✓] Pi-hole blocking is Enabled
[cont-init.d] 20-start.sh: exited 0.
[cont-init.d] done.
[services.d] starting services
Starting crond
[services.d] done.
Starting pihole-FTL (no-daemon) as root
Starting lighttpd

Startup is normally very quick, the slowness you are seeing is because the downloads are being blocked by something in your network.

[✗] Status: Connection Refused