thar-be-settings: log a render error when running in --all mode

[zmrow]

When running in --all mode, thar-be-settings (intentionally) does not fail
when a template fails to render. This commit logs a message
with the appropriate details in the event of a failure.

Issue #, if available:
Fixes #412

Description of changes:

• Add match statement to catch and log the Err() case.

Testing done:

Run thar-be-settings with a setting passed on the command line:

bash-5.0# thar-be-settings <<< '["settings.hostname"]'
Oct 17 16:18:29.582  INFO thar_be_settings: thar-be-settings started
Oct 17 16:18:29.584  INFO thar_be_settings: Parsing stdin for updated settings
Oct 17 16:18:29.586  INFO thar_be_settings: Requesting affected services for settings: {"settings.hostname"}
Oct 17 16:18:29.592  INFO thar_be_settings: Requesting configuration file data for affected services
Oct 17 16:18:29.597  INFO thar_be_settings: Rendering config files...
Oct 17 16:18:29.599  INFO thar_be_settings: Writing config files to disk...
Oct 17 16:18:29.600  INFO thar_be_settings: Restarting affected services...

Run thar-be-settings --all on a system where a few kubernetes settings don't exist:

bash-5.0# thar-be-settings --all
Oct 17 16:18:35.319  INFO thar_be_settings: thar-be-settings started
Oct 17 16:18:35.320  INFO thar_be_settings: Requesting configuration file data for affected services
Oct 17 16:18:35.329  INFO thar_be_settings: Rendering config files...
Oct 17 16:18:35.331  INFO thar_be_settings::config: Unable to render template 'kubernetes-ca-crt': RenderError { desc: "TemplateHelperError :: InvalidTemplateValue", template_name: Some("kubernetes-ca-crt"), line_no: Some(1), column_no: Some(1), cause: Some(InvalidTemplateValue { expected:}...SNIP...
Oct 17 16:18:35.336  INFO thar_be_settings::config: Unable to render template 'kubelet-kubeconfig': RenderError { desc: "Variable \"settings.kubernetes.api-server\" not found in strict mode.", template_name: Some("kubelet-kubeconfig"), line_no: Some(7), column_no: Some(14), cause: None }  
Oct 17 16:18:35.341  INFO thar_be_settings: Writing config files to disk...
Oct 17 16:18:35.342  INFO thar_be_settings: Restarting all services...

bash-5.0# echo $?
0

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[zmrow]

Updated per @tjkirch comments

[etungsten]

🎃