VOL-1460 Install protos and pyvoltha in venv properly

Change-Id: I6012f6951d3a583c2c0854f371dc20dfd5ba7212
diff --git a/python/Makefile b/python/Makefile
index 31846fc..27aec1d 100644
--- a/python/Makefile
+++ b/python/Makefile
@@ -136,7 +136,7 @@
 	mkdir -p voltha-protos/dist
 	cp ../../voltha-protos/dist/*.tar.gz voltha-protos/dist/
 	@ . ${VENVDIR}/bin/activate && \
-	    pip install pyvoltha/dist/*.tar.gz \
+	    pip install pyvoltha/dist/*.tar.gz && \
 	    pip install voltha-protos/dist/*.tar.gz
 endif