Make service unit test easier to debug

It's sort of hard to break into this function with gdb. Seperating it out
makes it a lot easier to work out where things are breaking.

Change-Id: If99effd44fe677452ac3c1012b99da7da80c720e
Reviewed-on: https://gerrit.libreoffice.org/8844
Reviewed-by: Chris Sherlock <chris.sherlock79@gmail.com>
Tested-by: Chris Sherlock <chris.sherlock79@gmail.com>