Fix type conversion error for RoiPooling.forward (#1078)
Fix type conversion error for RoiPooling.forward (#1078)

* fix type

* add forward

* clean

* add test back

intel-analytics/BigDL,yangw1234/BigDL,intel-analytics/BigDL,intel-analytics/BigDL,yangw1234/BigDL,yangw1234/BigDL,yangw1234/BigDL,intel-analytics/BigDL