Remove outdated test_forcesched that tests deprecated behaviour.

This test was using force_local and force_remote which are deprecated in the
pipeline version of disco.
Fix small issues in task_io to pass test_discoproto.

The test_discoproto used to fail because of these small issues.  It should
reliably pass now.
Fix test_query to create the necessary files on the master.

This test will only pass if the task is executed on the master where the input
files are available.  If the tasks are executed on other nodes, they will be
failed and retried.  Assuming that the master is also one of the worker nodes,
it will eventually succeed.
Merge pull request #397 from pooya/shayan/fix_tests

Shayan/fix tests