Adding connection type check for the exporter

[jingyuanli001]

A few weeks ago I was trying to use the weblogic monitoring exporter to export metrics from the Weblogic server. I went through an issue that when I was uploading the configuration file, I got 200 response code but the configuration was not updated (See #209 for details). It turns out to be a connection type mismatch, i.e. my weblogic server is using http connection but my exporter was using https. So I wonder if there is any way to make the exporter provide some error messages when the connection type is wrong rather than just give the 200 response code (to help locate the issue when necessary). Thanks! Tagging for visibility @russgold

[tbarnes-us]

@rjeberhard