Before this patch it was possible only to view list of graphs
that are related to cluster level of given env and no more.
Now graphs list for env is returning all graphs
related to it (release, plugins and cluster level).
Now the following commands are possible:
fuel2 graph list [--env ENV_ID] [--cluster] [--plugins] [--release]
All options working as filter narrowing list to the given environment
related graphs and/or graphs levels.
Change-Id: I006cf6767a9bf0d89af5026728bd13ddc42c4aa8
Partial-Bug: #1563851
Closes-Bug: #1621585