osd: Drop watchers from blacklisted clients

On blackist addition or populate ObjectContext
   check watcher address against blacklist
Add dout() of the watcher's ip address

fixes: #3527

Signed-off-by: David Zafman <david.zafman@inktank.com>
Fix usage of commands supported by TestOpsSocketHook::test_ops()

Signed-off-by: David Zafman <david.zafman@inktank.com>
Add dump_blacklist to admin socket

Signed-off-by: David Zafman <david.zafman@inktank.com>