Prevent infinite start/stop loop - initialize launcherFuture early

[BoykoAlex]

Naive and simple fix for #610

[BoykoAlex]

In case isActive() needs to be left alone as is, another option could be check isActive() || initializedFuture != null perhaps or perhaps brand new boolean flag isStarted which would become true when start() called and false when stop() is called as well as initially... Feedback is welcomed

[mickaelistria]

I don't see isActive modified in this patch. But I think it'd be OK to modify it if it's missing 1 condition.

[BoykoAlex]

isActive() looks at launcherFuture value... isActive() will start returning true sooner than it used to (which is a good thing i think) before lsp4j jsonrpc Launcher is started (ls to client connection established?). This is what i meant by the change to isActive() - implementation not changed but behaviour is changed.

Please see if this something that can be merged :-)