Only remove domain when FQDN is expected

[eyalkoren]

Fixes #2284

[apmmachine]

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• Start Time: 2021-11-25T13:27:19.210+0000

• Duration: 68 min 25 sec

• Commit: f1f0881

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Test	Results
Failed	0
Passed	2546
Skipped	21
Total	2567

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[SylvainJuge]

I've just found that there was another minor issue with using external commands, the output is not trimmed, thus locally I got (on linux) myhostname\n and it's sent as-is to apm-server 🤦.