VOL-1460 Updated to use a voltha-protos repo as source for protos

Change-Id: I6e88fb3bb16f91941abaad2f0a810ebc5aa29f36
diff --git a/python/requirements.txt b/python/requirements.txt
index 3e688c0..9a87401 100644
--- a/python/requirements.txt
+++ b/python/requirements.txt
@@ -65,3 +65,4 @@
 python-consul==0.6.2
 afkak==3.0.0.dev20181106
 pyvoltha==0.1.7
+voltha-protos==0.1.0