Avoid spurious "no body required" text in guides generated from wadl

When testing the @mediaType of representations, only look at the
end of the string to see if it ends with xml or json when deciding
if we have an xml or json representation.

Fix typo in spelling of pseduo-attribute on PI for suppressing
the "no response body" text:
<?rax-wadl skipNoResponseText="true"?>
(Was skipNoResponeText)

Change-Id: I885f60361728dfb9ed4e364e680dbf90d964612f
Closes-Bug: #1268723