I believe this is what you are looking for below....
In the MEE Console do the following:
1.) Locate the Device Group you are building your install sets from. 2.) Right click this group and go to properties. 3.) On the properties window that opens up, select General on the left side. (should already be selected) 4.) In the "Options" window scroll to the bottom and look for the check box labeled "Do not lock workstation if no user is authenticated" 5.) put a check in the box by this option and click "Apply" and then "Close" at the bottom 6.) Right click the device group again and choose "Reset all to group configuration" and say "Yes" to the warning message that pops up. 7.) Leave both check marks checked in the new window that pops up and click "OK"
You are now done. From now on, when the machine is syncing and no MEE user is authenticated it will not lock the workstation as you are seeing now.