ceph_manager: in test_map_discontinuity, delay killing osd for 20s
ceph_manager: in test_map_discontinuity, delay killing osd for 20s

This should give enough time for the replica to get the message
marking them clean.

Signed-off-by: Samuel Just <8c40222f34b9721b5d5709d4ed45337913ea1c3e@inktank.com>

ktdreyer/teuthology,robbat2/teuthology,ceph/teuthology,tchaikov/teuthology,dmick/teuthology,SUSE/teuthology,t-miyamae/teuthology,dreamhost/teuthology,caibo2014/teuthology,tchaikov/teuthology,SUSE/teuthology,zhouyuan/teuthology,michaelsevilla/teuthology,dreamhost/teuthology,yghannam/teuthology,ivotron/teuthology,dmick/teuthology,ivotron/teuthology,robbat2/teuthology,michaelsevilla/teuthology,caibo2014/teuthology,ktdreyer/teuthology,zhouyuan/teuthology,dmick/teuthology,SUSE/teuthology,ceph/teuthology,t-miyamae/teuthology,yghannam/teuthology