Update fan in / fan out test (no automatic copy) 📋
Update fan in / fan out test (no automatic copy) 📋

Now that we don't automatically copy the content of an input to an
output (when the same resource is used as both an input and an output),
this means that:
- Our fan-in / fan-out test will need to explicitly write to the output
  path, instead of writing to the input path and assuming it would get
  copied over (the very behaviour we're changing in #1188)
- Data previously written to an output that is used as an input, and
  then an output later on, will be lost unless explicitly copied. In the
  update to the examples this was handled by symlinking the input to the
  output, I decided to instead update the test to no longer expect to
  see a file that was written by the first task in the graph and to not
  copy it explicitly.

Note that there is actually a race between the two tasks fanning out -
if the were writing the same file we would not be able to reliably
predict which would win.

Part of fixing #1188

tektoncd/pipeline,tektoncd/pipeline