pytest warnings from sasmodels for opencl

[pkienzle]

The pytest command here:

$ pytest sasmodels/model_test.py::ellipsoid[opencl]

gives the following warnings:

sasmodels/model_test.py::ellipsoid[opencl]
  .../sasmodels/sasmodels/kernelcl.py:470: RepeatedKernelRetrieval: Kernel 'ellipsoid_Iq' has been retrieved more than once. Each retrieval creates a new, independent kernel, at possibly considerable expense. To avoid the expense, reuse the retrieved kernel instance. To avoid this warning, use cl.Kernel(prg, name).
    functions = [getattr(program, k) for k in names]

sasmodels/model_test.py::ellipsoid[opencl]
  .../sasmodels/sasmodels/kernelcl.py:470: RepeatedKernelRetrieval: Kernel 'ellipsoid_Iqxy' has been retrieved more than once. Each retrieval creates a new, independent kernel, at possibly considerable expense. To avoid the expense, reuse the retrieved kernel instance. To avoid this warning, use cl.Kernel(prg, name).
    functions = [getattr(program, k) for k in names]

sasmodels/model_test.py::ellipsoid[opencl]
  .../sasmodels/sasmodels/kernelcl.py:470: RepeatedKernelRetrieval: Kernel 'ellipsoid_Imagnetic' has been retrieved more than once. Each retrieval creates a new, independent kernel, at possibly considerable expense. To avoid the expense, reuse the retrieved kernel instance. To avoid this warning, use cl.Kernel(prg, name).
    functions = [getattr(program, k) for k in names]

It appears that the opencl compiler is being called multiple times. These warnings only appear for ellipsoid, cylinder, and sphere, which are the shapes which have a shape@structure test in their test suite.

[pkienzle]

Fixed by #677