change diag output yaml name

[rem1776]

Description
Changes the name of the output yaml table from diag_out.yaml to diag_manifest.yaml.

The change in diag_manager.F90 is just fixing a uninitialized return value that was setting off a runtime check.

How Has This Been Tested?
make check on the amd box

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published in downstream modules
• New check tests, if applicable, are included
• make distcheck passes

The base branch was changed.

[bensonr]

@rem1776 - is the intent to write out the input diag_table as a yaml? Or is it to list what variables will be output as part of a run - basically a catalog?

[rem1776]

This is only for the diag_manager rewrite, so it's mainly to show what was read in from the diag_table.yaml plus any additional information we may want for post processing.