(#3341) The classad cache depends on having the caller trim whitespace from strings
before calling Insert. This is arguably a bug in the cache code, but it's easier and
cheaper to fix in the compatibility layer, so this patch changes the convert-old-to-new
method to trim trailing whitespace.
The visible symptom of the bug is that reading ClassAds from a file takes about twice as
much CPU time as reading them off the wire because when read from a file, they have \n
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