added pinning for mcp repos, mk-apt and contrail

Change-Id: I3ca753e11290df0cf0727b3d8cbb18b2324c6f86
diff --git a/linux/system/repo/ubuntu.yml b/linux/system/repo/ubuntu.yml
index b4137bd..d36bcc1 100644
--- a/linux/system/repo/ubuntu.yml
+++ b/linux/system/repo/ubuntu.yml
@@ -3,19 +3,19 @@
     system:
       repo:
         ubuntu:
-          source: "deb http://archive.ubuntu.com/ubuntu/ ${_param:linux_system_codename} main restricted universe"
+          source: "deb [arch=amd64] http://archive.ubuntu.com/ubuntu/ ${_param:linux_system_codename} main restricted universe"
           architectures: amd64
           default: true
           key_id: 437D05B5
           key_server: keyserver.ubuntu.com
         ubuntu_updates:
-          source: "deb http://archive.ubuntu.com/ubuntu/ ${_param:linux_system_codename}-updates main restricted universe"
+          source: "deb [arch=amd64] http://archive.ubuntu.com/ubuntu/ ${_param:linux_system_codename}-updates main restricted universe"
           architectures: amd64
           default: true
           key_id: 437D05B5
           key_server: keyserver.ubuntu.com
         ubuntu_security:
-          source: "deb http://archive.ubuntu.com/ubuntu/ ${_param:linux_system_codename}-security main restricted universe"
+          source: "deb [arch=amd64] http://archive.ubuntu.com/ubuntu/ ${_param:linux_system_codename}-security main restricted universe"
           architectures: amd64
           default: true
           key_id: 437D05B5