Useless `Turn off` action for machines which `power type` are `manual`

MAAS 3.4 Stable (3.3.4) shows a Turn off action for the machine whose power is managed manually. This is useless and should be removed. It seems to be an outstanding issue as I also saw it from earlier versions.

Hi @maasuser1 ,

thank you for taking time to report bugs. Please follow this guide and report bugs only on launchpad.

If bugs are reported only here on discourse, they will get lost.

Thank you!