lib: make tst_detach_device_by_fd() also close dev_fd #151

Job	Run time
job (debian:stable, gcc, i386)	6m 34s
job (debian:stable, ppc64el, powerpc64le-linux-gnu-gcc, 1, out, cross-compile)	5m 8s
job (debian:stable, arm64, aarch64-linux-gnu-gcc, 1, out, cross-compile)	5m 11s
job (debian:stable, s390x, s390x-linux-gnu-gcc, 1, out, cross-compile)	4m 56s
job (alpine:latest, gcc, asciidoctor)	4m 44s
job (debian:stable, gcc, out, minimal)	4m 51s
job (opensuse/archive:42.2, gcc)	6m 16s
job (quay.io/centos/centos:stream9, gcc, asciidoc-pdf, out)	4m 40s
job (debian:testing, gcc, asciidoctor-pdf)	7m 2s
job (debian:oldstable, clang)	7m 29s
job (fedora:latest, clang, 1, asciidoctor-pdf)	6m 29s
job (opensuse/leap:latest, gcc, asciidoc-pdf)	5m 32s
job (debian:oldstable, gcc, asciidoctor)	6m 3s
job (debian:testing, clang, asciidoctor-pdf)	8m 34s
job (ubuntu:jammy, gcc, asciidoctor, out)	4m 13s
job (ubuntu:bionic, gcc, asciidoc-pdf)	5m 57s
	1h 33m 39s

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