Modify "use_param" functionality of MockHttp class to also work if provided
param is no available in every request.
Add get_secure_random_string utility function.
Unify argument order in crate_node: AWS, OpenStack

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Add ex_metadata parameter to create_node

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Add ex_get_metadata_for_node to AWS and OpenStack

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
type -> rtype.
Update CHANGES.