Retry package install to handle contention for apt lock

Change-Id: I88a3bc4e8d0720aac36beb311c506df3489300cb
diff --git a/roles/test-client-install/files/test-client-playbook.yml b/roles/test-client-install/files/test-client-playbook.yml
index 263cbec..7526cf4 100644
--- a/roles/test-client-install/files/test-client-playbook.yml
+++ b/roles/test-client-install/files/test-client-playbook.yml
@@ -9,6 +9,10 @@
         update_cache=yes
         cache_valid_time=3600
       become: yes
+      register: result
+      until: result | success
+      retries: 15
+      delay: 60
       with_items:
        - lxc