Let APT automatically choose the UCA/Pike-staging PPA architecture
based on current system architecture instead of hardcoding it.
Change-Id: I4fe645847ac0fb70a852477feba9f788fcb8da81
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
(cherry picked from commit 
9cac6117a760279b6be83034f5634f5505032cc0)
       repo:
         uca-staging:
           source: "deb http://ppa.launchpad.net/ubuntu-cloud-archive/${_param:openstack_version}-staging/ubuntu xenial main"
-          architectures: amd64
           key_id: 9F68104E
           key_server: keyserver.ubuntu.com
         uca:
           source: "deb http://ubuntu-cloud.archive.canonical.com/ubuntu xenial-updates/${_param:openstack_version} main"
-          architectures: amd64
           key_id: EC4926EA
           key_server: keyserver.ubuntu.com
       kernel:
 
         uca-staging:
           # yamllint disable rule:line-length
           source: "deb http://ppa.launchpad.net/ubuntu-cloud-archive/${_param:openstack_version}-staging/ubuntu xenial main"
-          architectures: amd64
           key_id: 9F68104E
           key_server: keyserver.ubuntu.com
           # yamllint enable rule:line-length
         uca:
           source: "deb http://ubuntu-cloud.archive.canonical.com/ubuntu xenial-updates/${_param:openstack_version} main"
-          architectures: amd64
           key_id: EC4926EA
           key_server: keyserver.ubuntu.com
       kernel: