Use the correct variable for the completion log message.

nixos/modules/update-deployment

@@ -88,8 +88,8 @@ export NIX_PATH="nixpkgs=$NIXPKGS_FOR_MORPH"
 # part.
 if morph deploy "${CHECKOUT}"/morph/grid/"${GRIDNAME}"/grid.nix switch --on "$(hostname)"; then
     # The deployment succeeded.  Record success along with context we pre-computed.
-    echo "${LOG} OK" >> ${HOME}/updates.txt
+    echo "${LOG_MESSAGE} OK" >> ${HOME}/updates.txt
 else
     # Oops.  Not so fortunate.  Record failure.
-    echo "${LOG} FAIL" >> ${HOME}/updates.txt
+    echo "${LOG_MESSAGE} FAIL" >> ${HOME}/updates.txt
 fi