Fix UUoC award warning for 'apt-key add -' [SC2002].
Fix UUoC award warning for 'apt-key add -' [SC2002].

It's no longer a UUoC, but apt-key is still deprecated,
so we'd better find a better solution.
Details: https://github.com/koalaman/shellcheck/wiki/SC2002

Signed-off-by: Diederik de Haas <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@cknow.org>

yodaaut/raspbian-ua-netinst