Connection timeout errors should result in a normal Exception with a stack trace

[morganmcc]

The FailedFuture implementation creates a failed future with a NoStackTraceThrowable error when created with a simple string message. This is the constructor that gets called by StompClientImpl:192 when there is a timeout waiting for a CONNECTED frame from the server. I think we need to create an actual failed future here with a logical Exception.

I ran into this because I was using the awaitResult construct in a Kotlin co-routine to make a call to connect to a Stomp server. The implementation of awaitResult looks for a failed future and then throws any error.

The consequences of this were that my code using awaitResult which was using a try/catch block with Exception failed to catch the error.

A connection error like this should result in a normal exception and not a Throwable. I changed things around to avoid using the awaitResult because of this.