Discover first free port for suave

[forki]

It seems sometimes the default port is occupied by another webserver.
We should discover the next free port and us that one.

/cc @jayp33 @haf

[haf]

That would probably be a good Utility method in Suave, which also is called from a static factory method in HttpBinding https://github.com/SuaveIO/suave/blob/master/src/Suave/Types.fs#L443.

[jayp33]

I can't reproduce the error. I assumed it had something to do with Tomcat, which was also running even though it didn't occupy the Suave port. On the second try it worked, having Tomcat running simultaneously.
Can't even reproduce the problem with a fresh clone of the repo.
Maybe I just pressed enter? ;-)

[forki]

yep. but I saw similar things before.