Use log.Printf for AWS poll errors to avoid mangled log lines

[saltzm]

Summary

The AWS IMDS poll loop logged failures with fmt.Printf("error during aws poll: %v", err) — no trailing newline and no timestamp, unlike every other log call in the codebase (which use log.Printf). The missing \n causes the error to run into the next log line, e.g.:

...connect: connection refused2026/07/18 13:12:51 http: TLS handshake error from ...

This is what made ~15 of these errors get mis-parsed in Datadog. Fix is a one-liner:

-  fmt.Printf("error during aws poll: %v", err)
+  log.Printf("error during aws poll: %v", err)

Context — this error is benign transient noise

Datadog (source:vprox, 7d): 228 hits across 148 distinct hosts, ≤6/host (~0.005% of polls); 170× IMDS 503 (throttling), 43× connection refused, clustered on fleet-wide blips. A failed poll originates in awsClient.GetAddresses(), which returns before any sm.Start/sm.Stop, so pollAws returns the previous IP set unchanged and just retries on the next 5s tick — it cannot drop a live tunnel (error starting new ip = 0 occurrences in 30d).

Unaddressed follow-ups (intentionally left out — judgment calls)

• Retry/backoff: IMDS client uses SDK default (3 attempts); could raise MaxAttempts / add a backoff retryer to trim 503 noise.
• Initial-poll tolerance: the startup poll aborts server launch on a transient IMDS blip (fail-fast); could retry instead.
• Metric: an aws_poll error counter would allow alerting on rates rather than eyeballing logs.

Link to Devin session: https://modal.devinenterprise.com/sessions/456280ed46e24e64a4e317cdb1c51dc9
Requested by: @saltzm

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