Fix closing of connection discarded by session target attrs #408

Job	Run time
test-postgres (9.5)	3m 30s
test-postgres (9.6)	2m 40s
test-postgres (10)	2m 52s
test-postgres (11)	2m 46s
test-postgres (12)	2m 41s
test-postgres (13)	2m 44s
test-postgres (14)	2m 38s
test-postgres (15)	2m 57s
test-platforms (3.7, ubuntu-latest, asyncio)	2m 21s
test-platforms (3.7, ubuntu-latest, uvloop)	2m 36s
test-platforms (3.7, macos-latest, asyncio)	3m 15s
test-platforms (3.7, macos-latest, uvloop)	2m 52s
test-platforms (3.7, windows-latest, asyncio)	4m 55s
test-platforms (3.8, ubuntu-latest, asyncio)	2m 31s
test-platforms (3.8, ubuntu-latest, uvloop)	2m 15s
test-platforms (3.8, macos-latest, asyncio)	3m 6s
test-platforms (3.8, macos-latest, uvloop)	3m 3s
test-platforms (3.8, windows-latest, asyncio)	5m 10s
test-platforms (3.9, ubuntu-latest, asyncio)	2m 8s
test-platforms (3.9, ubuntu-latest, uvloop)	2m 9s
test-platforms (3.9, macos-latest, asyncio)	4m 57s
test-platforms (3.9, macos-latest, uvloop)	2m 58s
test-platforms (3.9, windows-latest, asyncio)	4m 18s
test-platforms (3.10, ubuntu-latest, asyncio)	2m 27s
test-platforms (3.10, ubuntu-latest, uvloop)	2m 9s
test-platforms (3.10, macos-latest, asyncio)	2m 59s
test-platforms (3.10, macos-latest, uvloop)	2m 52s
test-platforms (3.10, windows-latest, asyncio)	4m 59s
test-platforms (3.11, ubuntu-latest, asyncio)	2m 21s
test-platforms (3.11, ubuntu-latest, uvloop)	2m 4s
test-platforms (3.11, macos-latest, asyncio)	3m 29s
test-platforms (3.11, macos-latest, uvloop)	3m 24s
test-platforms (3.11, windows-latest, asyncio)	4m 42s
Regression Tests	2s
	1h 42m 50s

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