In case of a config parameter error, report the client parameter name in...

...stead of the server parameter name. This is for issue #4121. 
Here is the output I got form a test:
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Sending the request to the server
Error contacting the server.
Server answered with: Invalid input parameter
Reason is: Invalid 'General.transferOutput' parameter
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The fix recognizes two kind of error messages:
1) "Parameter '<parname>'"
2) "'<parname>' parameter"
and replaces the <parname> by its client counterpart.
These two cases should cover most (if not all) of the InvalidParameter exception error messages that contain a parameter name (see src/python/WMCore/REST/Validation.py).