Configure htmlpurifier to use same directory permissions as Mahara (Bug #1333071)

This is needed to ensure the permissions of files/folders in dataroot
are correct for unit testing

Change-Id: I7877c22e0a5140e07d2c4fddaeb10e2f5ffc34ad
Signed-off-by: Simon Coggins <simon.coggins@totaralms.com>
Merge "Configure htmlpurifier to use same directory permissions as Mahara (Bug #1333071)"