lockdep: increase max locks (1000 -> 2000)

We hit the 1000 lock limit on

 ubuntu@teuthology:/a/teuthology-2014-08-31_02:30:01-rados-next-testing-basic-multi/463411

Fixes: #9309
Signed-off-by: Sage Weil <sage@redhat.com>
Merge pull request #2370 from ceph/wip-9309

lockdep: increase max locks (1000 -> 2000)

Reviewed-by: Loic Dachary <loic-201408@dachary.org>