Ability to provide SocketFactory for http client

[eblis]

Currently there's no way to provide a socket factory for the HttpClient used by Splunk.
In some scenarios - some example when running on a device with multiple networks, some connected to the internet while some without internet it is not possible to specify the correct network to use in order to have internet access.

It would be very nice if users of the library could reconfigure the httpClient to provide their own socket factory.

I've been trying to forcefully (i.e. via reflection) reconfigure the instance of httpClient to another one, but I've had limited success in actually getting the log messages to successfully send so far.