Add better error reporting to install_docker.sh

[Zalgo2462]

We should add set errexit and a bash trap to the install_docker.sh script in order to better diagnose runtime errors. In addition, all uses of curl should have the --fail flag so curl triggers the error trap if it hits a snag.

For an example, see install_beaker.sh https://github.com/activecm/BeaKer/blob/52eeea74b1b0eaf0705514755aab24155a62be9f/installer/stage/BeaKer/install_beaker.sh#L16