Un-namespace Python packages

Setuptools was updated and our hacky namespace-package-chickens came
back to roost. This removes the unsupported namespace package hacks.
diff --git a/src/python/grpcio_tests/commands.py b/src/python/grpcio_tests/commands.py
index 5ee551c..e822971 100644
--- a/src/python/grpcio_tests/commands.py
+++ b/src/python/grpcio_tests/commands.py
@@ -100,7 +100,7 @@
     pass
 
   def run(self):
-    import grpc.tools.protoc as protoc
+    import grpc_tools.protoc as protoc
 
     include_regex = re.compile(self.include)
     exclude_regex = re.compile(self.exclude) if self.exclude else None
@@ -116,7 +116,7 @@
     # but we currently have name conflicts in src/proto
     for path in paths:
       command = [
-          'grpc.tools.protoc',
+          'grpc_tools.protoc',
           '-I {}'.format(PROTO_STEM),
           '--python_out={}'.format(PROTO_STEM),
           '--grpc_python_out={}'.format(PROTO_STEM),
diff --git a/src/python/grpcio_tests/setup.py b/src/python/grpcio_tests/setup.py
index 01d5fa8..375fbd6 100644
--- a/src/python/grpcio_tests/setup.py
+++ b/src/python/grpcio_tests/setup.py
@@ -35,7 +35,7 @@
 
 import setuptools
 
-import grpc.tools.command
+import grpc_tools.command
 
 PY3 = sys.version_info.major == 3
 
@@ -68,7 +68,7 @@
     # Run `preprocess` *before* doing any packaging!
     'preprocess': commands.GatherProto,
 
-    'build_package_protos': grpc.tools.command.BuildPackageProtos,
+    'build_package_protos': grpc_tools.command.BuildPackageProtos,
     'build_py': commands.BuildPy,
     'run_interop': commands.RunInterop,
     'test_lite': commands.TestLite
diff --git a/src/python/grpcio_tests/tests/health_check/_health_servicer_test.py b/src/python/grpcio_tests/tests/health_check/_health_servicer_test.py
index 80300d1..5dde72b 100644
--- a/src/python/grpcio_tests/tests/health_check/_health_servicer_test.py
+++ b/src/python/grpcio_tests/tests/health_check/_health_servicer_test.py
@@ -27,14 +27,14 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-"""Tests of grpc.health.v1.health."""
+"""Tests of grpc_health.v1.health."""
 
 import unittest
 
 import grpc
 from grpc.framework.foundation import logging_pool
-from grpc.health.v1 import health
-from grpc.health.v1 import health_pb2
+from grpc_health.v1 import health
+from grpc_health.v1 import health_pb2
 
 from tests.unit.framework.common import test_constants
 
diff --git a/src/python/grpcio_tests/tests/protoc_plugin/_split_definitions_test.py b/src/python/grpcio_tests/tests/protoc_plugin/_split_definitions_test.py
index 64fd972..f8ae05b 100644
--- a/src/python/grpcio_tests/tests/protoc_plugin/_split_definitions_test.py
+++ b/src/python/grpcio_tests/tests/protoc_plugin/_split_definitions_test.py
@@ -44,7 +44,7 @@
 import unittest
 
 import grpc
-from grpc.tools import protoc
+from grpc_tools import protoc
 from tests.unit.framework.common import test_constants
 
 _MESSAGES_IMPORT = b'import "messages.proto";'
diff --git a/src/python/grpcio_tests/tests/reflection/_reflection_servicer_test.py b/src/python/grpcio_tests/tests/reflection/_reflection_servicer_test.py
index 87264cf..c7bfeae 100644
--- a/src/python/grpcio_tests/tests/reflection/_reflection_servicer_test.py
+++ b/src/python/grpcio_tests/tests/reflection/_reflection_servicer_test.py
@@ -27,14 +27,14 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-"""Tests of grpc.reflection.v1alpha.reflection."""
+"""Tests of grpc_reflection.v1alpha.reflection."""
 
 import unittest
 
 import grpc
 from grpc.framework.foundation import logging_pool
-from grpc.reflection.v1alpha import reflection
-from grpc.reflection.v1alpha import reflection_pb2
+from grpc_reflection.v1alpha import reflection
+from grpc_reflection.v1alpha import reflection_pb2
 
 from google.protobuf import descriptor_pool
 from google.protobuf import descriptor_pb2