fix routing issue for esoteric characters in gorilla/mux (#8967)

First step is to ensure that Path component is not decoded
by gorilla/mux to avoid routing issues while handling
certain characters while uploading through PutObject()

Delay the decoding and use PathUnescape() to escape
the `object` path component.

Thanks to @buengese and @ncw for neat test cases for us
to test with.

Fixes #8950
Fixes #8647

cmd/fs-v1_test.go

@@ -280,7 +280,7 @@ func TestFSDeleteObject(t *testing.T) {
 		t.Fatal("Unexpected error: ", err)
 	}
 	// Test with invalid object name
-	if err := fs.DeleteObject(context.Background(), bucketName, "\\"); !isSameType(err, ObjectNameInvalid{}) {
+	if err := fs.DeleteObject(context.Background(), bucketName, "\\"); !isSameType(err, ObjectNotFound{}) {
 		t.Fatal("Unexpected error: ", err)
 	}
 	// Test with object does not exist.