in_channels must equal to previous n_filter

[tiancheng2000]

Checklist

• I've read the Contribution Guidelines
• I've updated the documentation if necessary.
• I've tested that my changes are compatible with the latest version of Tensorflow.

Motivation and Context

Simple modification for rubustness of code. Otherwise all n_filters configured in a same layer_group must keep same, which is not neccessary.
Tested.

Description

Simple modification. Please refer to the diff.

[zsdonghao]

please update the changelog and make the travis pass

[tiancheng2000]

Travis-CI is complaining about RNN test failure, after I modified changelog?...

=========================== short test summary info ============================
FAILED tests/layers/test_layers_recurrent.py::Layer_RNN_Test::test_basic_simplernn_dropout_1
============ 1 failed, 229 passed, 10 warnings in 347.14s (0:05:47) ============