Because of quotas, there are times when creating a resource and then
deleting another resource may fail where doing it in the reverse order
would work, even though the resources are independent of one another.
When enqueueing 'check_resource' messages, send those for cleanup nodes
prior to those for update nodes. This means that all things being equal
(i.e. no dependency relationship), deletions will be started first. It
doesn't guarantee success when quotas allow, since only a dependency
relationship will cause Heat to wait for the deletion to complete before
starting creation, but it is a risk-free way to give us a better chance of
succeeding.
Change-Id: I9727d906cd0ad8c4bf9c5e632a47af6d7aad0c72
Partial-Bug: #1713900
09d74ffa3c