Double-serialization of string as input to durable activities

[andystaples]

When sending a string as an input to a Durable activity, we get double serialization - "Seattle" becomes ""Seattle""

Code:

    @FunctionName("HelloCities")
    public List<String> runOrchestrator(
            @DurableOrchestrationTrigger(name = "context") TaskOrchestrationContext ctx, 
            final ExecutionContext context) {
        return ctx.callActivity("SayHello", "Seattle", String.class).await();
    }

    @FunctionName("SayHello")
    public String sayHello(
            @DurableActivityTrigger(name = "name") String name,
            final ExecutionContext context) {
        context.getLogger().info("Saying hello to " + name + ".");
        return "Hello " + name + "!";
    }

Returns "Hello "Seattle""