Allow underscores in hostname #5097

Job	Run time
Unit tests with race condition detection	2m 50s
Lint	4m 23s
Unit Tests	2m 29s
Build Unsigned Snapshot	2m 5s
Performance Tests	4m 56s
Integration Tests (redhatenterprise, 9)	10m 29s
Integration Tests - Official OSS Images (bookworm, mainline, debian)	7m 28s
Integration Tests - Official OSS Images (bookworm, stable, debian)	7m 36s
Integration Tests (ubuntu, 22.04)	11m 0s
Integration Tests (alpine, 3.19)	7m 43s
Integration Tests - Official OSS Images (alpine, stable, alpine)	7m 16s
Integration Tests - Official Plus Images (alpine, 3.19, r31, alpine, /nginx-plus/agent)	7m 29s
Integration Tests - Official Plus Images (alpine, 3.20, r32, alpine, /nginx-plus/agent)	7m 32s
Integration Tests - Official Plus Images (debian, bookworm, r31, debian, /nginx-plus/agent)	8m 5s
Integration Tests - Official Plus Images (debian, bookworm, r32, debian, /nginx-plus/agent)	7m 56s
Integration Tests - Official OSS Images (alpine, mainline, alpine)	7m 20s
Load Tests	5m 1s
	1h 51m 38s

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