main: Shift iosched verification upward
main: Shift iosched verification upward

There's a block of CLI options sanity checks in the beginning of
main starting lambda, it's better to have the iosched validation
in this block.

Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla