pool: add log messages on connect error #253

Job	Run time
run-tests-ce (1.20, 1.10, false, false)	4m 32s
run-tests-ce (1.20, 2.8, false, false)	4m 28s
testing_mac_os (1.20, macos-11, brew)	12m 58s
run-tests-ce (1.20, 2.10, false, false)	4m 49s
testing_mac_os (1.20, macos-11, 1.10.15)	11m 47s
run-tests-ce (1.20, master, false, false)	10m 35s
testing_mac_os (1.20, macos-12, brew)	4m 51s
run-tests-ce (stable, 1.10, false, false)	4m 35s
testing_mac_os (1.20, macos-12, 1.10.15)	7m 31s
run-tests-ce (stable, 2.8, false, false)	4m 30s
testing_mac_os (stable, macos-11, brew)	14m 4s
run-tests-ce (stable, 2.10, false, false)	4m 56s
testing_mac_os (stable, macos-11, 1.10.15)	16m 21s
run-tests-ce (stable, master, false, false)	10m 47s
testing_mac_os (stable, macos-12, brew)	5m 50s
testing_mac_os (stable, macos-12, 1.10.15)	5m 12s
run-tests-ce (master, true, 1.20)	12m 2s
run-tests-ce (master, true, 1.20, false)	10m 24s
	2h 30m 12s

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