'Reading <host/scheme> metadata' logging message repeated twice when capgen-v1 called from CAM-SIMA

[nusbaume]

Description

when capgen-v1 is run it writes the messages Reading host metadata: and Reading scheme metadata: to the logger, which itself goes to stdout. For most of the routines in capgen-v1 it checks if the caller is providing its own python log, and then uses that to write messages. However, for the _load_metadata_files() routine it only uses the internal _LOGGER variable, which in the case of CAM-SIMA was pointing to the same stream as CIME's logger, resulting in the Reading XYZ metadata messages being written twice each time.

This bug can be fixed by simply updating _load_metadata_files to use a host-provided logger when it exists, which is the same strategy that other capgen-v1 routines use.

A PR is incoming.

Steps to Reproduce

1. Use the head of the feature/capgen-v1 branch (e.g. hash 09ae1d7) in CAM-SIMA.
2. Create a case with any physics suite.
3. Run case.setup in the case directory.
4. Run preview_namelists in the case directory, which triggers the code generation step for capgen-v1
5. Examine the messages being printed to the screen, and notice the ones that are being repeated twice each time.

Additional Context

I am guessing this issue is only present when using CAM-SIMA as it would only appear when using the python interface. The CLI is likely fine.