Basic validation for gerritbot/channels.yaml
Basic validation for gerritbot/channels.yaml

Recently a change merged that had not branches line and gerritbot
refused to start again. This could have been avoided by validation of
the file.

Test some basic validation of the yaml file to avoid breakage.

Change-Id: I2dc4a28aeac07d3fc73d3954d8fbe8f2448334e5

dongwenjuan/project-config,noorul/os-project-config,dongwenjuan/project-config,openstack-infra/project-config,noorul/os-project-config,Tesora/tesora-project-config,openstack-infra/project-config,Tesora/tesora-project-config