Connection Timeout is set to 15000000 Milliseconds on Non Windows Platforms

In non-blocking mode, the poll() is expecting timeout in milliseconds. Currently we the connection timeout as 15 seconds but the timeout given to the poll() is 15000000 milliseconds due to the timeout unit in microseconds passed to the connect() function.

https://github.com/couchbasedeps/sockpp/blob/aa7c52855630fe4b65ab7a7ebace10f1a15df030/src/connector.cpp#L111

I have noticed that while working on network interface feature as there are some BuiltInWebSocket objects leaked after the replicator is stopped after timeout & retry.