1869 ips not retrieve seqnode from cache

Fixed the issue where IPS do not retrieve sequence node content from Cache due to changes in the sequence node identifier message sent by AMC.

*HOW TO TEST*
Run brixserver.js locally (until the cloud is updated) and open page using the testpage-1div.xhtml with the parameters:

    ?assignment=test.sanvan.assign.mcq1a&activity=test.sanvan.activity.mcq1a

You may need to modify the local setting of testpage-1iv.xhtml to point the dev ams if you cannot run it locally.  

When you look at the IPS log and search for fromCache, the first page load should say "false." 
When the page is re-loaded, the IPS log should have an entry about sequence retrieval saying fromCache "true"

Also added a minor improvement on /log endpoint to accept 'r' parameter for rotating index.
Now you can open <ips>/log?r=0

@seannives could you code review. Thanks.