Only use curl --retry-connrefused when supported #1697

Job	Run time
Rust nightly on Linux	13s
Rust beta on Linux	15s
Rust stable on Linux	4s
Rust 1.62.0 on Linux	9s
Rust stable 18 months ago on Linux	10s
Rust stable minus 8 releases on Linux	11s
Rust nightly on macOS	15s
Rust beta on macOS	15s
Rust stable on macOS	19s
Rust 1.62.0 on macOS	22s
Rust stable 18 months ago on macOS	12s
Rust stable minus 8 releases on macOS	16s
Rust nightly on Windows	32s
Rust beta on Windows	34s
Rust stable on Windows	1m 6s
Rust 1.62.0 on Windows	28s
Rust stable 18 months ago on Windows	23s
Rust stable minus 8 releases on Windows	25s
Rust 1.0.0 on Linux	16s
	6m 25s

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