[DE37] Poor error reporting on failed key install for apt repo

[jcannava]

the script is not checking to see if the key is installed and the process then fails when attempting to 'apt-get update'. A simple check on the return status and an error message would prevent needless debugging.

[andymcc]

Although apt-get update should never have been run (since set -e is enabled the failure of apt-key command will kill the script) - I've added a line to make that clear and explicitly exit 1. https://github.com/rcbops/opencenter-install-scripts/pull/164