Bugfix #1910 main_v4.1 EnsembleStat level in forecast input template

[georgemccabe]

See #1910 for details.

Pull Request Testing

• Describe testing already performed for these changes:
  

Ran a modified version of EnsembleStat.conf basic use case that references {level?fmt=%2H} in the forecast input template and confirmed that it sets it to 0 even if the FCST_VAR1_LEVELS value is not.
Made changes and reran use case to confirm that it works as expected.

• Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
  

Run use case config saved for this PR using the latest release and with the bugfix branch to confirm that the change fixed the issue.

Text file with commands to run can be found on seneca here:
/d1/projects/METplus/pull_requests/METplus-4.1.0/bugfix_1910_main_v4.1/commands_to_run.txt

Run using the v4.1 release found in /usr/local, which should fail
The output will be written to /d1/personal/${USER}/1910-out-main

/usr/local/METplus/ush/run_metplus.py \
/d1/projects/METplus/pull_requests/METplus-4.1.0/bugfix_1910_main_v4.1/EnsembleStat_level.conf \
config.OUTPUT_BASE=/d1/personal/${USER}/1910-out-main

Run using the bugfix branch, which should succeed
The output will be written to /d1/personal/${USER}/1910-out-bugfix

/d1/projects/METplus/pull_requests/METplus-4.1.0/bugfix_1910_main_v4.1/METplus/ush/run_metplus.py \
/d1/projects/METplus/pull_requests/METplus-4.1.0/bugfix_1910_main_v4.1/EnsembleStat_level.conf \
config.OUTPUT_BASE=/d1/personal/${USER}/1910-out-bugfix

• Do these changes include sufficient documentation updates, ensuring that no errors or warnings exist in the build of the documentation? [Yes]

• Do these changes include sufficient testing updates? [Yes]

There was not an easy way to add a unit test for this fix because of the way the code was written. The changes for the develop branch will include a unit test to ensure that the correct behavior occurs

• Will this PR result in changes to the test suite? [No]
  

• Please complete this pull request review by 11/4/2022.
  

Pull Request Checklist

See the METplus Workflow for details.

• Add any new Python packages to the METplus Components Python Requirements table.
• Review the source issue metadata (required labels, projects, and milestone).
• Complete the PR definition above.
• Ensure the PR title matches the feature or bugfix branch name.
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  Select: Reviewer(s)
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  Select: Milestone as the version that will include these changes
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• After the PR is approved, merge your changes. If permissions do not allow this, request that the reviewer do the merge.
• Close the linked issue and delete your feature or bugfix branch from GitHub.

[j-opatz]

I verified that I received the same results as the prompt suggested: the v4.1 fails to find any files, while the bugfix branch ran successfully.