main: Be more verbose if quitting early from misconfiguration

[ebblake]

If the driver lacks support for usefully running the health monitor, be verbose by default about why we are exiting. The resulting logs will be handy in pointing the driver developer what thy might have done wrong in their CSI implementation, even if they didn't pass in a non-default --v=2.

Fixes: #305

What type of PR is this?
/kind bug

What this PR does / why we need it:
Make it easier for CSI driver developers to learn if they are using this sidecar incorrectly (for example, if the driver forgot to expose a feature this sidecar relies on).

Which issue(s) this PR fixes:

Fixes #305

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

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