Backport of docker_logger: reorder imports to save memory into release/1.3.x

[hc-github-team-nomad-core]

Backport

This PR is auto-generated from #14875 to be assessed for backporting due to the inclusion of the label backport/1.3.x.

The below text is copied from the body of the original PR.

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Nomad runs one logmon process and also one docker_logger process for each running allocation. A naive look at memory usage shows 10-30 MB of RSS, but a closer look shows that most of this memory (ex. all but ~2MB for logmon) is shared (Shared_Clean in Linux pmap).

But a heap dump of docker_logger shows that it currently has an extra ~2500 KiB of heap (anonymously-mapped unshared memory) used for init blocks coming from the agent code (ex. mostly regexes from go-version, structs, and the Consul SDK). The packages for running logmon, docker_logger, and executor have an init block that parses os.Args to drop into their own logic, which prevents them from loading all the rest of the agent code and saves on memory, so this was unexpected.

It looks like we accidentally reordered the imports in main to undo some of the work originally done in 404d2d4. This changeset restores the ordering. A follow-up heap dump shows this saves ~2MB of unshared RSS per docker_logger process.

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