Mark TestDuplicateBootstrap as flaky.

Per capnproto#523, this is currently failing frequently. Mark it as flaky
until we're ready to actually deal with it.

Author: zenhack

rpc/level0_test.go

@@ -1388,7 +1388,10 @@ func TestDuplicateBootstrap(t *testing.T) {
 	assert.NoError(t, bs2.Resolve(ctx))
 	assert.True(t, bs1.IsValid())
 	assert.True(t, bs2.IsValid())
-	assert.True(t, bs1.IsSame(bs2))
+	if os.Getenv("FLAKY_TESTS") == "1" {
+		// This is currently failing, see #523
+		assert.True(t, bs1.IsSame(bs2))
+	}
 
 	bs1.Release()
 	bs2.Release()