Added a --nowatch (with aliases --no-watch and --no-auto-restart) option to mysqld_safe that causes it to exit after
spawning mysqld.  We don't need mysqld_safe to restart mysqld after a crash, because systemd can do that just fine.

Based on code from Maarten Vanraes

scripts/mysqld_safe.sh:
  Added option --nowatch (with aliases --no-watch and --no-auto-restart)