[Merge] ~nteodosio/update-manager:installnow-oracular into update-manager:ubuntu/oracular

[Dave Jones]

Review: Approve

This change is already merged for plucky. This commit backports the change to affected series; approving and sponsoring
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https://code.launchpad.net/~nteodosio/update-manager/+git/update-manager/+merge/479159
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