Allow to configure insecure in clients_heat section

Exaclty this value is also defining whether standard usage of
OS::Heat::WaitConditionHandle form inside the instance's user data
will verify Heat server certificates.

Setting this to 'True' will make it possible to use WaitCondition
resources when Heat API is using self-signed certificates which can not
be validated by default CA bundles baked into cloud images.
However this will also have a side-effect of OS::Heat::Stack resource
not validating the certificate of the remote Heat service (e.g. in
another region).

Change-Id: I4667ae6f7e26704c98480362f14fe74e23905fc3
3 files changed