It looks like the code left this as a todo, but the basic solution is to
add an extra parameter to BKE_bose_rest to check whether bones
are selected before reseting them.
I also corrected the operator description which said it acted on only
selected bones even when there is an option to turn that off. The
"act on selected" is generally implied for Blender's operators anyway.
Differential Revision: https://developer.blender.org/D8319
d42530824e