Fix missing time functions initialization in redis-benchmark

Commit 08e4226e596d35d3d0f3f094b4a9dd94e6f9ba99 broke redis-benchmark.

Made time function initialization automatic on first execution.
Added explicit initialization of time functions in redis-benchmark, to
avoid additional cost on first benchmark execution.
Merge commit 'c94db2ba3849ffe2ae1b3da04bd2860a601afcd5' into release-2.8.17

Conflicts:
	bin/release/redis-2.8.17.zip