[FAB-11763] Improve unit tests for channel_test
[FAB-11763] Improve unit tests for channel_test

func TestChannelPull(t *testing.T)   should confirm two proto.SignedGossipMessages.

Change-Id: If7fc50d12aadc364adb1e8129ba82ef76213aff7
Signed-off-by: ping40 <3fdcdb40e75d7c7b82676a72401288e08659651a@gmail.com>

stemlending/fabric,stemlending/fabric,muralisrini/fabric,xixuejia/fabric,xixuejia/fabric,jimthematrix/fabric,manish-sethi/fabric-sidedb,manish-sethi/fabric-sidedb,manish-sethi/fabric,hyperledger/fabric,binhn/fabric,xixuejia/fabric,manish-sethi/fabric-sidedb,manish-sethi/fabric-sidedb,muralisrini/fabric,muralisrini/fabric,jimthematrix/fabric,manish-sethi/fabric-sidedb,manish-sethi/fabric-sidedb,stemlending/fabric,hyperledger/fabric,manish-sethi/fabric-sidedb,binhn/fabric,manish-sethi/fabric,stemlending/fabric,binhn/fabric