No functional change.

Call my_timer_init() only once and then reuse it from InnoDB and
perfschema storage engines.

This patch speeds up empty test for me like this:
./mtr -mem innodb.kevg,xtradb  1.21s user 0.84s system 34% cpu 5.999 total
./mtr -mem innodb.kevg,xtradb  1.12s user 0.60s system 31% cpu 5.385 total