Close discovery service socket before exiting #1927

Job	Run time
build	9m 54s
build-ceph	2m 1s
demo	3m 42s
pytest (cli)	2m 11s
discovery (container)	4m 16s
ha (sanity)	3m 46s
discovery (embedded)	4m 4s
pytest (cli_change_lb)	2m 37s
ha (state_transitions)	3m 48s
pytest (state)	2m 10s
ha (state_transitions_both_gws)	4m 15s
pytest (multi_gateway)	2m 33s
ha (state_transitions_loop)	11m 13s
pytest (server)	2m 38s
pytest (grpc)	2m 49s
ha (state_transitions_rand_loop)	15m 3s
pytest (omap_lock)	13m 7s
ha (late_registration)	3m 50s
pytest (old_omap)	2m 20s
ha (late_registration_loop)	16m 21s
pytest (log_files)	3m 12s
ha (4gws)	5m 41s
pytest (nsid)	3m 42s
ha (4gws_loop)	7m 16s
ha (namespaces)	9m 57s
ha (namespaces_loop)	17m 20s
ha (mtls)	3m 54s
ha (notify)	2m 32s
push-images-to-ceph-registry	0s
push-images-to-private-registry	0s
	2h 46m 12s

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