Remove inputs from provided config

[choffee]

We keep our config in one file and so filters, inputs and outputs are all defined. It would be good if LFV could strip out the inputs before running the tests. If you do define an input then I found that the process just hangs around waiting for the input and never terminates.

[magnusbaeck]

This would indeed be nice, but do you have any ideas of how to accomplish in a robust fashion without writing a full lexer and parser for Logstash's configuration language? I don't think the effort of doing that is proportional to the benefit.