[MXAPPS-581] Move notebooks requiring multi-gpus.

Move two notebooks requiring multi-GPUs out of the single GPU test suite.

tests/nightly/straight_dope/test_notebooks_multi_gpu.py

@@ -38,6 +38,10 @@ def setUpClass(self):
     def test_multiple_gpus_gluon(self):
         assert _test_notebook('chapter07_distributed-learning/multiple-gpus-gluon')
 
+    # TODO(vishaalk): Do a dry run, and then enable.
+    #def test_training_with_multiple_machines(self):
+    #    assert _test_notebook('chapter07_distributed-learning/training-with-multiple-machines')
+
     # Chapter 8
 
     # TODO(vishaalk): Module skimage needs to be added to docker image.

tests/nightly/straight_dope/test_notebooks_single_gpu.py

@@ -32,10 +32,12 @@
     'chapter01_crashcourse/introduction',
     'chapter01_crashcourse/chapter-one-problem-set',
     'chapter02_supervised-learning/environment',
+    'chapter07_distributed-learning/multiple-gpus-scratch',
+    'chapter07_distributed-learning/multiple-gpus-gluon',
+    'chapter07_distributed-learning/training-with-multiple-machines'
 ]
 
 
-
 class StraightDopeSingleGpuTests(unittest.TestCase):
     @classmethod
     def setUpClass(self):
@@ -226,15 +228,6 @@ def test_adam_gluon(self):
     def test_hybridize(self):
         assert _test_notebook('chapter07_distributed-learning/hybridize')
 
-    # TODO(vishaalk): module 'mxnet.gluon' has no attribute 'autograd'
-    #def test_multiple_gpus_scratch(self):
-    #    assert _test_notebook('chapter07_distributed-learning/multiple-gpus-scratch')
-
-    def test_multiple_gpus_gluon(self):
-        assert _test_notebook('chapter07_distributed-learning/multiple-gpus-gluon')
-
-    def test_training_with_multiple_machines(self):
-        assert _test_notebook('chapter07_distributed-learning/training-with-multiple-machines')
 
     # Chapter 8