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/src/test/utils/CordLogger.py b/src/test/utils/CordLogger.py
index cc1845b..1efe086 100644
--- a/src/test/utils/CordLogger.py
+++ b/src/test/utils/CordLogger.py
@@ -170,7 +170,7 @@
            serverDetails = cls.serverOptionsList
         stat_choice = 'COLLECTD'
         test_name = cls.testHostName
-        test_image = 'cord-test/nose'
+        test_image = 'cordtest/nose'
         if stat_choice in stat:
            onos_ctrl = OnosCtrl('org.onosproject.cpman')
            status, _ = onos_ctrl.activate()
@@ -222,4 +222,3 @@
         if stat_choice in stat:
             onos_ctrl = OnosCtrl('org.onosproject.cpman')
             status, _ = onos_ctrl.deactivate()
-