fuzzy: increase operation count for each fsstress invocation

fuzzy: increase operation count for each fsstress invocation

For online fsck stress testing, increase the number of filesystem
operations per fsstress run to 2 million, now that we have the ability
to kill fsstress if the user should push ^C to abort the test early.
This should guarantee a couple of hours of continuous stress testing in
between clearing the scratch filesystem.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>