rewind images after write
rewind images after write

after sinkdisc or sinkmemory, we need to rewind the image we wrote to so
that subsequent reads get the written image and don't regenerate it

mcanthony/libvips,lovell/libvips,mcanthony/libvips,leiyangyou/libvips,jcupitt/libvips,lovell/libvips,jcupitt/libvips,leiyangyou/libvips,lovell/libvips,mcanthony/libvips,leiyangyou/libvips,jcupitt/libvips,lovell/libvips,jcupitt/libvips,leiyangyou/libvips,mcanthony/libvips