tf-generator: Remove test_data in job.yaml when --testplan is not provided

[Artur-at-work]

Add --provisionOnly flag (Default=False) to generate job.yaml without default test_data stage. Use case if when need to only provision the DUT without test plan.

Test: Provision only: ./testflinger_yaml_generator.py -c 202405-33980 -o prov-new.yaml --provisionType url --provisionImage http://10.131.60.220:8080/job/somerville-noble-oem-24.04a/lastSuccessfulBuild/artifact/out/somerville-noble-oem-24.04a-20240820-71.iso --provisionToken ~/testflinger/test-yaml/jenkins-token.txt --provisionAuthKeys ~/testflinger/test-yaml/authorized_keys --provisionUserData ~/testflinger/test-yaml/user-data --provisionOnly

Test default plan only without provision: ./testflinger_yaml_generator.py -c 202405-33980 -o prov-new.yaml

Provision and test default plan: ./testflinger_yaml_generator.py -c 202405-33980 -o prov-new.yaml --provisionType url --provisionImage http://10.131.60.220:8080/job/somerville-noble-oem-24.04a/lastSuccessfulBuild/artifact/out/somerville-noble-oem-24.04a-20240820-71.iso --provisionToken ~/testflinger/test-yaml/jenkins-token.txt --provisionAuthKeys ~/testflinger/test-yaml/authorized_keys --provisionUserData ~/testflinger/test-yaml/user-data

[Artur-at-work]

@seankingyang could you help to review please?

[Artur-at-work]

@seankingyang thanks for the feedback, please help to review again.