Move openolt_grpc.py to grpc directory

Change-Id: Icaaa2312d6f933d2b05d9c27c9ea72d68ca698c5
diff --git a/voltha/adapters/openolt/openolt_grpc.py b/voltha/adapters/openolt/grpc/openolt_grpc.py
similarity index 100%
rename from voltha/adapters/openolt/openolt_grpc.py
rename to voltha/adapters/openolt/grpc/openolt_grpc.py
diff --git a/voltha/adapters/openolt/openolt_device.py b/voltha/adapters/openolt/openolt_device.py
index 5aab531..0c751aa 100644
--- a/voltha/adapters/openolt/openolt_device.py
+++ b/voltha/adapters/openolt/openolt_device.py
@@ -168,7 +168,7 @@
         # FIXME - better way that avoids absolute paths?
         self._grpc = subprocess.Popen(
             ['python',
-             'voltha/voltha/adapters/openolt/openolt_grpc.py',
+             'voltha/voltha/adapters/openolt/grpc/openolt_grpc.py',
              self.broker,
              self.host_and_port],
             env={'PYTHONPATH': '/voltha:/voltha/voltha/protos/third_party'})