Support for binary cloud-init user data

[TheRealFalcon]

Cloud-init has support for certain forms of binary user data, but LXD doesn't pass it along correctly.

For example, with the following user data:

$ cat cloud-config.yaml                      
#cloud-config
bootcmd:
 - echo 'hi' > /var/tmp/hi

If I

gzip cloud-config.yaml

then

lxc launch ubuntu:jammy asdf -c user.user-data="$(cat cloud-config.yaml.gz)"

the data received from inside the container using

curl --unix-socket /dev/lxd/sock http://1.0/1.0/config/user.user-data

doesn't match the data contained in cloud-config.yaml.gz

It appears the data is getting cutoff at a null byte.