Lazy ByteQ perf test was printing ReadFails twice

Instead of supplying q.WriteFails() then q.ReadFails() to the
printTimings(...) function we were sending q.ReadFails() twice.
Changed printTimings(...) to printSummary(..)

Because the method takes the number of failed reads and writes it no
longer prints just timing info. So the name was outmoded.
readFail -> readFails, writeFail -> failedWrites

The variables readFail, writeFail and the methods commonQ.ReadFails(),
commonQ.WriteFails() were awkward to read. They have been replaced with
more natural names.