bump gRPC version to 1.2.0

- updated Protouf to 3.2.0, which gRPC 1.2.0 depend on

Change-Id: If63d468c867680c3e57a36a37ba878b1daeb69ae
diff --git a/incubator/protobuf-dependencies/pom.xml b/incubator/protobuf-dependencies/pom.xml
index 2feff8a..6f3a8ba 100644
--- a/incubator/protobuf-dependencies/pom.xml
+++ b/incubator/protobuf-dependencies/pom.xml
@@ -30,7 +30,7 @@
     <url>http://onosproject.org</url>
 
     <properties>
-        <protobuf.version>3.0.0</protobuf.version>
+        <protobuf.version>3.2.0</protobuf.version>
     </properties>
 
     <dependencies>