find_stale_locks(): Only query locked nodes
find_stale_locks(): Only query locked nodes

Simple performance oversight.

Signed-off-by: Zack Cerza <d7cdf09fc0f0426e98c9978ee42da5d61fa54986@redhat.com>

dreamhost/teuthology,SUSE/teuthology,dmick/teuthology,caibo2014/teuthology,robbat2/teuthology,SUSE/teuthology,ktdreyer/teuthology,SUSE/teuthology,dmick/teuthology,robbat2/teuthology,ceph/teuthology,ceph/teuthology,ktdreyer/teuthology,dmick/teuthology,dreamhost/teuthology,caibo2014/teuthology