Remove no-longer-needed loop in ExecGather().

Remove no-longer-needed loop in ExecGather().

Coverity complained quite properly that commit ea15e1867 had introduced
unreachable code into ExecGather(); to wit, it was no longer possible to
iterate the final for-loop more or less than once.  So remove the for().

In passing, clean up a couple of comments, and make better use of a local
variable.