rbd-mirror: fix race preventing local image deletion

rbd-mirror: fix race preventing local image deletion

On primary image deletion, a race between InstanceReplayer::release_image()
(which calls ImageReplayer::stop())and ImageReplayer::handle_bootstrap()
may prevent the non-primary image from being deleted. Because
ImageReplayer::handle_bootstrap() checks if the start has been canceled
before processing -ENOLINK, m_delete_requested is not set to true and the
local image is not deleted.
This commit sets m_delete_requested to true before checking if the
start has been canceled to ensure that the image is deleted during shut_down,
and updates ImageReplayer::bootstrap() to cancel the BootstrapRequest
and prevent a potentially long time spent in an image sync if ImageReplayer
stop is requested.

Fixes:  https://tracker.ceph.com/issues/61672
Signed-off-by: N Balachandran <nibalach@redhat.com>