Fix roundtripping issue

[valenting]

This fixes a regression from #1021

#[test]
fn test_parse_url_with_single_byte_control_host() {
    let input = "l://\x01:";

    let url1 = Url::parse(input).unwrap();
    let url2 = Url::parse(url1.as_str()).unwrap();
    assert_eq!(url2, url1);
}

The problem is that the code at:

rust-url/url/src/host.rs

Lines 157 to 161 in 22b925f

	match utf8_percent_encode(&input, CONTROLS).into() {
	Cow::Owned(v) => Cow::Owned(v),
	// if we're borrowing, then we can return the original Cow
	Cow::Borrowed(_) => input,
	},

assumed Cow::Borrowed means no percent-encoding happened, but for single byte controls we do get a Cow::Borrowed from the static encoding table

[emilio]

Maybe it should just check input.len() == v.len()? Comparing the whole string seems a bit unfortunate.