Rework loadbalancer server selection logic #1546

Job	Run time
build / Build	7m 6s
Docker Tests (basics)	59s
E2E Tests (startup)	9m 9s
Docker Tests (bootstraptoken)	51s
E2E Tests (s3)	7m 57s
Docker Tests (cacerts)	49s
E2E Tests (btrfs)	5m 13s
Docker Tests (compat)	2m 37s
E2E Tests (externalip)	4m 38s
Docker Tests (lazypull)	53s
E2E Tests (privateregistry)	6m 18s
Docker Tests (upgrade)	2m 32s
E2E Tests (embeddedmirror)	5m 16s
E2E Tests (wasm)	5m 15s
	59m 33s

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