Fix downloading of craftbukkit when using 1.16.5

[Paulomart]

The previous logic attempted to download craftbukkit from 1. This resulted in a 404.
This commit adjusts this logic and uses the alternative download site at 2.

---

Verifying the fix

Current logic

docker run --rm -it -e EULA=true -e TYPE=craftbukkit -e VERSION=1.16.5 itzg/minecraft-server:java8
[init] Running as uid=1000 gid=1000 with /data as 'drwxrwxrwx    2 1000     1000          4096 Nov 24 20:37 /data'
[init] Resolved version given 1.16.5 into 1.16.5
[init] Resolving type given craftbukkit
[init] Downloading CraftBukkit from https://download.getbukkit.org/craftbukkit/craftbukkit-1.16.5.jar ...
curl: (22) The requested URL returned error: 404 Not Found

Updated logic

docker run --rm -it -e EULA=true -e TYPE=craftbukkit -e VERSION=1.16.5 mc-multiarch
[init] Running as uid=1000 gid=1000 with /data as 'drwxrwxr-x 2 1000 1000 4096 Dec  2 15:39 /data'
[init] Resolved version given 1.16.5 into 1.16.5
[init] Resolving type given craftbukkit
[init] Downloading CraftBukkit from https://cdn.getbukkit.org/craftbukkit/craftbukkit-1.16.5.jar ...
[init] Creating server.properties in /data/server.properties
[init] Disabling whitelist
[init] Setting whitelist to 'false' in /data/server.properties
[init] Setting white-list to 'false' in /data/server.properties
[init] Setting enable-rcon to 'true' in /data/server.properties
[init] Setting rcon.password to 'minecraft' in /data/server.properties
[init] Setting rcon.port to '25575' in /data/server.properties
[init] Setting motd to 'A Craftbukkit Minecraft Server powered by Docker' in /data/server.properties
[init] Checking for JSON files.
[init] Setting initial memory to 1G and max to 1G
[init] Starting the Minecraft server...
Unsupported Java detected (61.0). Only up to Java 15 is supported.

[itzg]

Wow, just that one combo of craftbukkit? Thanks for the fix.

[itzg]

This has now been merged and published to all the image variants.

[Paulomart]

@itzg Yeah, I guess they uploaded it wrong. I've tested all other variants with vanilla, craftbukkit and spigot from 1.8 thou 1.18: This was the only one having issues.

Thanks for the quick merge :)