Update npm version before running npm commands in basebuild file

Change-Id: I7c6c1ec864b1729db0ff8b9c66753e643a10955c
diff --git a/packer/provision/basebuild.sh b/packer/provision/basebuild.sh
index 36857b6..4ef2637 100644
--- a/packer/provision/basebuild.sh
+++ b/packer/provision/basebuild.sh
@@ -43,6 +43,7 @@
         zip
         # end of apt-get install list
 
+    npm install -g npm@latest # update npm to latest version, since apt doesn't fetch latest
     npm install -g bower
     npm install karma --save-dev