Don't set the color variables if tput is not available, not working, or
if ncolors < 8.
Move the color variables outside of eval to avoid calling tput over and
over again.
Change-Id: Id51a742b77ad0f7c99c1c7c5d05bed0f423b75de
[ROCm/roctracer commit: 993dcf9503]
Laurent Morichetti
690df5dfcb