Cast messages will not contain a msg_id and we're currently
sending messages to the default excahgne with empty msg_id.
In order to fix it we should not send replies if there is no
msg_id in message.
Change-Id: I5b1142029d2c718c3929cf6cf1f6e958b95a5c96
Closes-bug: #1355058
Even in case of libraries and when they are not big like nova.
It is better to use next rules:
1) structure of tests directory is the same as a root of project
Tests directory will be well organized, and it will be simple to find
where to write tests
2) names for end modules should be test_<name_of_testing_module>.py
Change-Id: I75b4b3df4fffc8dfe389c547ae7a004d1b278ecc
