Allow for @HystrixCommand to be used on parameterized return type

[sawano]

The current implementation of hystrix-javanica doesn't work with methods that have a parameterized method return type. I.e. the following (somewhat silly example) would not work:

@HystrixCommand
public <T> T echo(T value) {
    return value;
}

This is because the code that determines the execution type from the method return type incorrectly matches Object to Future and then marks it for asynchronous execution. This leads to an exception at runtime. E.g.:

final String answer = echo("hello");

would cause a class cast exception.

Correcting the logic for determining the execution type fixes this issue.

[cloudbees-pull-request-builder]

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[sawano]

This build seems to inherit a test failure from previous builds.