Send all VPC CNI logs to /dev/null by default

[RobertLucian]

Without this PR, the following lines would constantly get printed on screen when the cortex CLI is run:

2022-09-09 16:59:13.481063827 +0000 UTC m=+0.039526031 write error: can't make directories for new logfile: mkdir /host: permission denied
2022-09-09 16:59:13.481448123 +0000 UTC m=+0.039910297 write error: can't make directories for new logfile: mkdir /host: permission denied

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checklist:

• run make test and make lint
• test manually (i.e. build/push all images, restart operator, and re-deploy APIs)

[jshahbazi]

Just a heads-up: I'm still running into this in v0.42.1 on macOS. Setting the env variable as per the PR fixes it.