Pull cord-tester images from dockerhub as they are available now on dockerhub.
Change image names to be compatible with dockerhub image names.
Update prerequisites.sh last step to pull all the cord-tester docker images.
This should make the cord-test.py build all step redundant now since images should be available for testing immediately after prerequisites.sh are run.

Change-Id: I64cf664a214924349d6728ca2a52974decdef47f
diff --git a/roles/prereq/tasks/main.yml b/roles/prereq/tasks/main.yml
index 55918b2..58fd316 100644
--- a/roles/prereq/tasks/main.yml
+++ b/roles/prereq/tasks/main.yml
@@ -85,7 +85,7 @@
   become: yes
   docker:
     name: cord-test
-    image: "{{ docker.registry }}/cord-test/nose:{{ docker.image_version }}"
+    image: "{{ docker.registry }}/cordtest/nose:{{ docker.image_version }}"
     pull: always
     state: absent
 
@@ -93,7 +93,7 @@
   become: yes
   docker:
     name: cord-radius
-    image: "{{ docker.registry }}/cord-test/radius:{{ docker.image_version }}"
+    image: "{{ docker.registry }}/cordtest/radius:{{ docker.image_version }}"
     pull: always
     state: absent
 
@@ -101,7 +101,7 @@
   become: yes
   docker:
     name: cord-quagga
-    image: "{{ docker.registry }}/cord-test/quagga:{{ docker.image_version }}"
+    image: "{{ docker.registry }}/cordtest/quagga:{{ docker.image_version }}"
     pull: always
     state: absent