getpart.pm: make test definition section/part parser more robust

getpart.pm: make test definition section/part parser more robust

Test definition section parts which needed to include xml-lingo as contents
of that part required that the xml-blurb was written as a single line. Now the
xml-data inside the part can be written multiline making it more readable.

Tested with <client><file> part which is written to disk before <command> runs.