path_rrdcheck_log is concatenated into the args passed to exec_background(),
which does not escape string args, so a shell metacharacter would inject a
command. No settings form exposes this value today, so this is defense in
depth and a forward-port of the release/1.2.31 fix.
Refs #7473
Signed-off-by: Thomas Vincent <thomasvincent@gmail.com>
