The following worked for me:
Open "System Preferences", select "Keyboard", then "Shortcuts".
From the list of shortcut categories in the left-hand list, select "App Shortcuts".
Add (this is counter-intuitive since you want to disable an existing shortcut) a new shortcut using the "+" button:
Under "Menu Title", enter "Lock Screen" (this should be how the action appears on the "Apple" desktop menu).
Then under Keyboard Shortcut, enter a key combination that you can "sacrifice". You could use something hard to type like Ctrl + Alt + Cmd + Shift + L.
You "save" the new Keyboard Shortcut (which actually overrides the previously invisible Ctrl + Cmd + Q shortcut) by closing the Keyboard preferences window.
Now you should be able to enjoy Ctrl + Cmd + Q's awesome Emacs binding again.