Default values for compute's global fields are overriding the ones set statically (through config file)

[orviz]

Short Description of the issue

If a default value is set for a global field inside static.get_compute_endpoint_defaults(), this value is overriding the one set in the YAML configuration file. If this bug gets confirmed, any global field set by the user within compute is being ignored.

Environment

• Operating System: Debian 10
• python version: 3.9.1
• OpenStack version: Rocky

Steps to reproduce

E.g. setting a value for total_ram global field:

compute:
  total_ram: 600

results in:

GLUE2CloudComputingManagerTotalRAM: 0

However, if set under endpoints:defaults the result is the expected one. In the current OpenStack sample the field is at the compute level, not at the endpoint level, so it really looks like a bug.

Summary of proposed changes

The priority (lower to higher) should be: defaul values -> static values -> dynamic values

The current logic implemented for obtaining the static info and merging it with the dynamic one is rather burdensome & difficult to follow (_get_what(), get_defaults_from_yaml(), get_fields_and_prefix(), populate_default_values(), ..). Besides, once the default & static info is obtained, the dynamic info relies once again on the defaults (by calling openstack.get_compute_endpoints_defaults() method) from the static provider.

It would be better to move to a plain simple solution, even though this implies that some of the current magic is removed from the code. Built-in python solutions like collections.defaultdict can reduce substantially the current implementation.