Reading kv-store-prefix from ENV

Change-Id: I50c57fc473fab0385e0ac120d03d584e97046df7
diff --git a/requirements.txt b/requirements.txt
index b49f951..67751ba 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -18,4 +18,4 @@
 structlog==19.2.0
 transitions==0.6.4
 txaioetcd==0.3.0
-voltha-protos==3.4.2
+voltha-protos==4.0.5