string_test: The dark side of coverity

Me: "Mr Coverity, I thought I fixed the dead code warning just few days ago in
this file. Why are you still complaining about the same stuff to me?"

Mr. Coverity: "Duh! But you are supposed to fix all occurences in the same file."

Me: "Mr. Coverity, I didn't see you flag the warning in the other places last
time?"

Mr. Coverity: "Shh! That is the secret of my dark side!"

Change-Id: I565eccd90bf1bb39c9881664d361f83396ca8bcc
Signed-off-by: Steven Luong <sluong@cisco.com>