Keyboard shortcut mapping for Ctrl+Alt+Del in Parallels
I did not find an answer to the base question, but I did locate a sufficiently good workaround.  Karabiner offers finer-grained control of keys than OSX's keyboard settings, including the ability to add exceptions to key switching.  I used these settings:

Karabiner -&gt; Change Key
    Change Command_L Key -&gt; Command_L to Control_L (except Virtual Machine, RDC)
    Change Control_L Key -&gt; Control_L to Command_L (except Virtual Machine, RDC)


Now all of the Ctrl keyboard shortcuts I am accustomed to work in both OSX and my VMs.