rados/thrashers: enable split testing

Signed-off-by: Samuel Just <sam.just@inktank.com>
task yaml for basic upgrade

Signed-off-by: tamil <tamil.muthamizhan@inktank.com>
fs: drop fuse_use_invalidate_cb: true, since that is now the default

Signed-off-by: Sage Weil <sage@inktank.com>