Refactor UpdateMessageSubscriptions in CCmpRangeOverlayRenderer

Introduced in rP20622

rewrite 3 ifs to 1 if
merge 2 member variables into 1 member variable
remove 2 function local variables
save one call for CComponentManager as both ifs would or execute or not

code is shorter and looks nicer

Differential Revision: D3009
Reviewed by: bb