Fetch ONOS dependencies everytime we build

Change-Id: Ibba1403f13ee89b42631a4e1d416e6c831a27389
diff --git a/build.gradle b/build.gradle
index 5064cf5..92d4a87 100644
--- a/build.gradle
+++ b/build.gradle
@@ -103,7 +103,7 @@
 
 task buildOnosApps (type: Exec) {
     workingDir './apps'
-    commandLine 'mvn', 'clean', 'install'
+    commandLine 'mvn', 'clean', 'install', '-U'
 }
 
 task copyLocalRepo (dependsOn: buildOnosApps, type: Exec) {