fix(http1): send 'connection: close' during graceful shutdown #2859

Job	Run time
Check Style	7s
semver	16s
Verify hyper.h is up to date	11s
Test with Miri	2m 30s
features	33s
minimal-versions	37s
Test C API (FFI)	17s
Check MSRV	24s
udeps	24s
Test stable on ubuntu-latest	1m 0s
Test stable on windows-latest	1m 22s
Test stable on macOS-latest	1m 15s
Test beta on ubuntu-latest	1m 3s
Test beta on windows-latest	1m 23s
Test beta on macOS-latest	1m 8s
Test nightly on ubuntu-latest	1m 22s
Test nightly on windows-latest	1m 23s
Test nightly on macOS-latest	1m 22s
Build docs	0s
Check exposed types	0s
CI is green	0s
	16m 37s

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