Need to fix the bug in bbox sampling of SSD.
Created by: qingqing01
Refer https://github.com/weiliu89/caffe/commit/6feb7d99d3c6938321c9afd21d8f397a7a33b0a4
Created by: qingqing01
Refer https://github.com/weiliu89/caffe/commit/6feb7d99d3c6938321c9afd21d8f397a7a33b0a4