MULE-6916: Update Saxon version to 9.1.0.8

_  Re-adding fix
(cherry picked from commit 2a01987)
MULE-6916: Update Saxon version to 9.1.0.8

_Forcing tests to use xalan's transformer factory implemetation to avoid broken tests.

NOTE: mule already uses xalan when run in standalone mode as xalan is loaded as endorsed library. There is no need to change the wrapper conf files.