(fix) install ssh to base image

[abeyum]

What this PR does / why we need it:
When attempting to clone a repository from within the docker images we encountered the error pasted below. In order to connect to github, we need the appropriate ssh credentials passed in via a env variable SSH_AUTH_SOCK. We aren't using file based ssh keys, instead we are using an ssh agent which is then shared with the container. Unfortunately, the ability to ssh is missing, hence this pull request.

Error: Command "git clone --recursive --depth=1 --branch=development [email protected]:<owner>/<repo>git /project/.garden/sources/module/app--61c96b198b" failed with code 128:
--
Cloning into '/project/.garden/sources/module/app--61c96b198b'...
error: cannot run ssh: No such file or directory
fatal: unable to fork

Which issue(s) this PR fixes:
n/a

Special notes for your reviewer:
n/a

[edvald]

Nice and simple :) Thanks @abeyum!