Fix race condition in tests, fix URI bug

- Some tests can't be run in parallel.
- `URI` had a pointer to `RequestHeader` which was updated with
`RequestHeader.CopyTo` which resulted in the URI pointing to the wrong
`RequestHeader` causing bugs and race conditions.

The only reason `URI` contained a pointer to `RequestHeader` was to delay the
call to `RequestHeader.Host()` until really needed. But these days instead
of parsing all headers, `RequestHeader.Host()` uses
`RequestHeader.peekRawHeader()` which is rather fast. So we can remove the
pointer in `URI` and completely decouple the two structs improving code
quality and fixing the bug.

For some reason this results in faster code on average as well:
benchmark                                          old ns/op     new ns/op     delta
BenchmarkClientGetEndToEnd1Inmemory-8              1189          1369          +15.14%
BenchmarkClientGetEndToEnd10Inmemory-8             1143          1161          +1.57%
BenchmarkClientGetEndToEnd100Inmemory-8            1228          1236          +0.65%
BenchmarkClientGetEndToEnd1000Inmemory-8           1213          1213          +0.00%
BenchmarkClientGetEndToEnd10KInmemory-8            1362          1350          -0.88%
BenchmarkClientEndToEndBigResponse1Inmemory-8      139967        130070        -7.07%
BenchmarkClientEndToEndBigResponse10Inmemory-8     142233        131809        -7.33%
BenchmarkServerGet1ReqPerConn-8                    1726          1593          -7.71%
BenchmarkServerGet2ReqPerConn-8                    882           927           +5.10%
BenchmarkServerGet10ReqPerConn-8                   440           436           -0.91%
BenchmarkServerGet10KReqPerConn-8                  341           339           -0.59%
BenchmarkServerPost1ReqPerConn-8                   1728          1706          -1.27%
BenchmarkServerPost2ReqPerConn-8                   968           963           -0.52%
BenchmarkServerPost10ReqPerConn-8                  506           505           -0.20%
BenchmarkServerPost10KReqPerConn-8                 424           420           -0.94%
BenchmarkServerGet1ReqPerConn10KClients-8          1117          1051          -5.91%
BenchmarkServerGet2ReqPerConn10KClients-8          565           514           -9.03%
BenchmarkServerGet10ReqPerConn10KClients-8         390           387           -0.77%
BenchmarkServerGet100ReqPerConn10KClients-8        355           348           -1.97%
BenchmarkServerHijack-8                            339           348           +2.65%
BenchmarkServerMaxConnsPerIP-8                     326           325           -0.31%
BenchmarkServerTimeoutError-8                      24355         24180         -0.72%

1 files changed, 4 insertions, 2 deletions

diff --git a/fs_test.go b/fs_test.go
index 5d53f68..19d1f30 100644
--- a/fs_test.go
+++ b/fs_test.go
@@ -435,6 +435,8 @@ func testParseByteRangeError(t *testing.T, v string, contentLength int) {
 }
 
 func TestFSCompressConcurrent(t *testing.T) {
+	// This test can't run parallel as files in / might by changed by other tests.
+
 	fs := &FS{
 		Root:               ".",
 		GenerateIndexPages: true,
@@ -465,7 +467,7 @@ func TestFSCompressConcurrent(t *testing.T) {
 }
 
 func TestFSCompressSingleThread(t *testing.T) {
-	t.Parallel()
+	// This test can't run parallel as files in / might by changed by other tests.
 
 	fs := &FS{
 		Root:               ".",
@@ -525,7 +527,7 @@ func testFSCompress(t *testing.T, h RequestHandler, filePath string) {
 		t.Fatalf("unexpected error when gunzipping response body: %s. filePath=%q", err, filePath)
 	}
 	if string(zbody) != body {
-		t.Fatalf("unexpected body %q. Expected %q. FilePath=%q", zbody, body, filePath)
+		t.Fatalf("unexpected body len=%d. Expected len=%d. FilePath=%q", len(zbody), len(body), filePath)
 	}
 }