fix a bug in conv_ops_test.py by handling ndims==2 case for conv bwd input
fix a bug in conv_ops_test.py by handling ndims==2 case for conv bwd input

gunan/tensorflow,gunan/tensorflow,gunan/tensorflow,gunan/tensorflow,gunan/tensorflow,gunan/tensorflow,gunan/tensorflow,gunan/tensorflow,gunan/tensorflow,gunan/tensorflow,gunan/tensorflow,gunan/tensorflow