pillar/devicenetwork: fix goroutine leak #9075

Job	Run time
packages (buildjet-4vcpu-ubuntu-2204-arm, arm64)	4m 8s
packages (buildjet-4vcpu-ubuntu-2004, amd64)	3m 40s
packages (buildjet-4vcpu-ubuntu-2004, riscv64)	1m 49s
eve (arm64, xen, generic)	9m 33s
eve (arm64, kvm, generic)	9m 13s
eve (amd64, xen, generic)	8m 51s
eve (amd64, kvm, generic)	6m 49s
eve (amd64, kubevirt, generic)	9m 47s
eve (riscv64, mini, generic)	3m 8s
eve (amd64, kvm, rt)	8m 45s
eve (arm64, kvm, nvidia)	7m 57s
eve (arm64, kvm, imx8mp_pollux)	7m 34s
eve (arm64, kvm, imx8mp_epc_r3720)	7m 42s
	1h 28m 56s

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