This PR improves the handling of additional properties of the JavaCXFClientCodegen and the corresponding tests.

Currently, when using the jaxrs-cxf-client generator without explicitly setting useGzipFeatureForTests and useLoggingFeatureForTests a warning is logged for each of these properties, saying: The value (generator's option) must be either boolean or string. Default to false. The behavior is fixed in this MR.

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the shell script ./bin/generate-samples.shto update all Petstore samples related to your fix. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. For Windows users, please run the script in Git BASH.
• If contributing template-only or documentation-only changes which will change sample output, build the project beforehand.
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cc: @bbdouglas @sreeshas @jfiala @lukoyanov @cbornet @jeff9finger @karismann @Zomzog @lwlee2608 @bkabrda