rbd-replay: Use standard image@snap instead of image/snap

Signed-off-by: Adam Crume <adamcrume@gmail.com>
rbd-replay: Add rbd_replay::rbd_loc

Signed-off-by: Adam Crume <adamcrume@gmail.com>
rbd-replay: Switch ImageNameMap to using rbd_loc

Signed-off-by: Adam Crume <adamcrume@gmail.com>
rbd-replay: Switch ImageNameMap from regex to plain string matching

Signed-off-by: Adam Crume <adamcrume@gmail.com>