remove the DIALOG_NO_PARENT abomination and replace it with a flags
parameter

Change-Id: I71b7dc46c619f2db56af6d4dc2c17daf0a2c8534
Reviewed-on: https://gerrit.libreoffice.org/15645Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>