rtsold: Add -i to the usage message
PR: 266634
Fixes: 231bac4ccc43 ("rtsol/rtsold: Add option to skip random delay")
MFC after: 1 week
(cherry picked from commit 9e9e64b693ab1e08cca46e26e468160542c33f3a)
(cherry picked from commit c4380d5b9383e2a062840573b36ab643b65b2610)