Build should fail if new uncovered items are introduced

[tethryus]

From @Bonczidai on April 4, 2017 13:40

04:00:36 [INFO] ------------------------------------------------------------
04:00:36 [INFO] Following 173 executables do not have tests:
04:00:36 [INFO] - io.cloudslang.amazon.aws.ec2.deploy_instance
04:00:36 [INFO] - io.cloudslang.amazon.aws.ec2.instances.check_instance_state
04:00:36 [INFO] - io.cloudslang.amazon.aws.ec2.reboot_instance
04:00:36 [INFO] - io.cloudslang.amazon.aws.ec2.start_instance
04:00:36 [INFO] - io.cloudslang.amazon.aws.ec2.stop_instance
04:00:36 [INFO] - io.cloudslang.amazon.aws.ec2.undeploy_instance

<new uncovered item>
<new uncovered item>

Copied from original issue: CloudSlang/cs-content#957

[levice14]

this (moving the issue) is arguable - the builder is stateless, I would prefer to keep it that way - IMHO the CI system should use the builder for generating the report and then calc the diff -- but there quite a few ways we can achieve this