Handle unset execution conf in jobs service

[teamurko]

Summary

Fixed code to handle null execution conf field in JobConf

Changes

• [ ] Client-facing API Changes
• [ ] Internal API Changes
• [x] Bug Fixes
• [ ] New Features
• [ ] Performance Improvements
• [ ] Code Style
• [ ] Refactoring
• [ ] Documentation
• [x] Tests

For all the boxes checked, please include additional details of the changes made in this pull request.

Testing Done

• [x] Manually Tested on local docker setup. Please include commands ran, and their output.
• [ ] Added new tests for the changes made.
• [x] Updated existing tests to reflect the changes made.
• [ ] No tests added or updated. Please explain why. If unsure, please feel free to ask for help.
• [ ] Some other form of testing like staging or soak time in production. Please explain.

docker compose --profile with_jobs_scheduler run openhouse-jobs-scheduler -  --type SNAPSHOTS_EXPIRATION --cluster local --tablesURL http://openhouse-tables:8080 --jobsURL http://openhouse-jobs:8080
...
2024-06-03 17:52:53 2024-06-04 00:52:53 INFO  OtelConfig:70 - initializing open-telemetry sdk
2024-06-03 17:52:54 2024-06-04 00:52:54 INFO  Reflections:219 - Reflections took 153 ms to scan 1 urls, producing 4 keys and 10 values
2024-06-03 17:52:54 2024-06-04 00:52:54 INFO  JobsScheduler:108 - Starting scheduler
2024-06-03 17:52:54 2024-06-04 00:52:54 INFO  JobsScheduler:130 - Fetching task list based on the job type: SNAPSHOTS_EXPIRATION
2024-06-03 17:53:01 2024-06-04 00:53:01 INFO  OperationTasksBuilder:29 - metadata: dbName: db, tableName: test, creator: openhouse
2024-06-03 17:53:01 2024-06-04 00:53:01 INFO  JobsScheduler:140 - Submitting and running 1 jobs based on the job type: SNAPSHOTS_EXPIRATION
2024-06-03 17:53:01 2024-06-04 00:53:01 INFO  OperationTask:71 - Launching job for dbName: db, tableName: test, creator: openhouse
2024-06-03 17:53:06 2024-06-04 00:53:06 INFO  OperationTask:97 - Launched a job with id SNAPSHOTS_EXPIRATION_db_test_15c49365-2bb3-4ba6-89ae-5ce396ad67c0 for dbName: db, tableName: test, creator: openhouse
...
2024-06-03 17:58:42 2024-06-04 00:58:42 INFO  OperationTask:143 - Finished job for entity dbName: db, tableName: test, creator: openhouse: JobId SNAPSHOTS_EXPIRATION_db_test_15c49365-2bb3-4ba6-89ae-5ce396ad67c0, executionId 0, runTime 47116, queuedTime 17212, state SUCCEEDED
2024-06-03 17:58:42 2024-06-04 00:58:42 INFO  JobsScheduler:182 - Finishing scheduler for job type SNAPSHOTS_EXPIRATION, tasks stats: 1 created, 1 succeeded, 0 cancelled (timeout), 0 failed, 0 skipped (no state)

For all the boxes checked, include a detailed description of the testing done for the changes made in this pull request.

Additional Information

• [ ] Breaking Changes
• [ ] Deprecations
• [ ] Large PR broken into smaller PRs, and PR plan linked in the description.

For all the boxes checked, include additional details of the changes made in this pull request.