enable --compat flag by default (#9326)

if needed use --no-compat to disable md5sum while
verifying any performance numbers.

bring back --compat behavior as default to avoid
additional documentation and confusing behavior,
as we are working towards improving md5sum to
be faster on AVX instructions, enabling this
should be hardly a problem in future versions
of MinIO.

fixes #8012
fixes #7859
fixes #7642

cmd/gateway/b2/gateway-b2.go

@@ -87,8 +87,13 @@ EXAMPLES:
 
 // Handler for 'minio gateway b2' command line.
 func b2GatewayMain(ctx *cli.Context) {
+	strictS3Compat := true
+	if ctx.IsSet("no-compat") || ctx.GlobalIsSet("no-compat") {
+		strictS3Compat = false
+	}
+
 	minio.StartGateway(ctx, &B2{
-		strictS3Compat: ctx.IsSet("compat") || ctx.GlobalIsSet("compat"),
+		strictS3Compat: strictS3Compat,
 	})
 }