CBLT-316:  hack around short-comings of XML::Simple, which was
munging the xml that this script is not interested in, so now we
just peel off all unrelated xml into strings, and do the parsing
and replacing only of 'hudson.model.StringParameterDefinition'
parts.

Change-Id: If3c697b511f6513fbbe9c5ee4b72ad88de6e2902
Reviewed-on: http://review.couchbase.org/38153
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>