Fix problems when using SSH keys with a non-root users.

[fago]

I'm using the CLI image with a SSH key set via environment variable. However this is currently not possible as non root.

I got it working with a line like

RUN /lagoon/entrypoints/05-ssh-key.sh && chown -R 1000:1000 /home/.ssh
in the dockerfile, but since the key file is made readonly this errors out on repeated runs. 600 should be just as safe (owner can change it anyway) and makes starting the container work.

TL/DR to repeat the problem:

• Add the line above the add the key
• Start the container as non-root user with the environment variable being still set

Result:

• Error due to /home/.ssh/key being not writable anymore.

The PR fixes the problem.