led chaser with non-mechanical shut-off option
The HCT4017 already has everything you need to turn off the LEDs.    

Just interface your MCU to the MR (master reset) line, this will enable you to turn off all the Q(1-9) outputs simultaneously. It does mean that you can't use Q0 of course, since that would be ON when reset. 

Since your MCU is going to be less than 6-9V capable you do need to isolate the higher voltage drive. 

Perhaps something like this:







simulate this circuit &ndash; Schematic created using CircuitLab

Update: as pointed out not using digit "0" causes a pause in the chaser cycle. I included a fix for this by adding Q3