Add IConsulAgent interface for mocking in unittests

If this version is beign used, expected code changes are:

Before

var consulKVStore *kvStore.ConsulAgent

After

var consulKVStore kvStore.IConsulAgent

What's Changed

• add is trace sampled flag in logs by @cw-balaji in #207
• add interface to mock consul kv store by @cw-balaji in #216

Full Changelog: v1.14.0...v1.15.0