Adds new endpoint /deployments to Murano, to enable
Murano Dashboard to get all deployments for all environments.
This is needed in order to improve log browsing for
deployments, which calls for creating a new view in which
all deployments across all environments can be viewed.
Also made deployment unit tests more robust.
Partially-implements: blueprint improve-deployment-log-browsing
Change-Id: I1b6a313af1a0c4aa57bd4e6f51da92b396b35165