Fix and refine keras tests (#2176)
Fix and refine keras tests (#2176)

* test

* fix

* update

* fix style

* update tests

* update upsampling2d test

* meet review

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