Pin voltha-protos to 1.0.0

Change-Id: I67f2b1d127d584624287bf15f161c74ae0d1f268
diff --git a/python/requirements.txt b/python/requirements.txt
index b264018..71cbeed 100644
--- a/python/requirements.txt
+++ b/python/requirements.txt
@@ -59,5 +59,5 @@
 pexpect==4.6.0
 python-consul==0.6.2
 afkak==3.0.0.dev20181106
-voltha-protos>=0.1.4
+voltha-protos==1.0.0
 pyvoltha==0.2.4