fix(http1): send 'connection: close' during graceful shutdown #2858

Job	Run time
Verify hyper.h is up to date	13s
semver	13s
Check Style	5s
features	32s
Check MSRV	24s
Test C API (FFI)	18s
minimal-versions	28s
Test with Miri	2m 28s
Test stable on ubuntu-latest	59s
udeps	20s
Test stable on windows-latest	1m 0s
Test stable on macOS-latest	1m 12s
Test beta on ubuntu-latest	1m 9s
Test beta on windows-latest	1m 0s
Test beta on macOS-latest	1m 8s
Test nightly on ubuntu-latest	1m 14s
Test nightly on windows-latest	59s
Test nightly on macOS-latest	1m 16s
Check exposed types	0s
Build docs	0s
CI is green	0s
	14m 58s

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