Don't test conda.recipe/run_test.py with py.test
Don't test conda.recipe/run_test.py with py.test

Before, when running py.test from the dask root directory, py.test would
try to "test" the conda.recipe/run_test.py file, and fail, since it is
not for unit-tests.

cowlicks/dask,ssanderson/dask,blaze/dask,chrisbarber/dask,wiso/dask,jayhetee/dask,wiso/dask,mraspaud/dask,dask/dask,PhE/dask,jakirkham/dask,mikegraham/dask,ContinuumIO/dask,mrocklin/dask,gameduell/dask,PhE/dask,vikhyat/dask,vikhyat/dask,dask/dask,jayhetee/dask,jcrist/dask,mrocklin/dask,cpcloud/dask,clarkfitzg/dask,jakirkham/dask,ContinuumIO/dask,pombredanne/dask,clarkfitzg/dask,jcrist/dask,pombredanne/dask,blaze/dask,ssanderson/dask,mraspaud/dask