[NET-381] Reduce log level of a msg from Error to Warn

[gabrielseibel1]

Describe your changes

I reduced log level of a msg from Error to Warn because it was appearing too frequently and it was not actually indicating a problematic situation.

Provide link to Netmaker PR if required

Provide testing steps

Run netclient joining a network
Observe "failed to check for endpoint on peer" is not printed frequently.

Checklist before requesting a review

• My changes affect only 10 files or less.
• I have performed a self-review of my code and tested it.
• If it is a new feature, I have added thorough tests, my code is <= 1450 lines.
• If it is a bugfix, my code is <= 200 lines.
• My functions are <= 80 lines.
• I have had my code reviewed by a peer.
• My unit tests pass locally.
• Netclient & Netmaker are awesome.

[CLAassistant]

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