Safety checks + conservative mount defaults

Added some safety checks

• Check that ioc git repo is public before cloning (fixes indefinite hanging bug for non-public repos)
• Only source env.sh from ioc repo if it exists (removes env.sh requirement from ioc repo)
• Only mount the main e3 lab share on /epics. (This is likely to be the people want to use/change. They can add others as needed)

approved this merge request

mentioned in commit c16867e1

merged