Connect should not be called twice on clients or compoments without disconnecting first. While this worked in some cases, mixing connect options, specifically first trying without, and then with a bosh_url, would lead to asserts being triggered. The connect logic now checks whether there's already a connection in progress or established, and raises a Lua exception early if there is. Test-Information: Tested on macOS 10.13 Connected components and clients with invalid and valid hosts, and with valid and invalid bosh_urls, all with and without disconnecting in between attempts. No asserts were triggered, and appropriate Lua exceptions were thrown. Change-Id: I6b91b57945844bce7fce0073e5d0fe199ab815d5