Refactor check_status_of_command_line_tools

[sivkovic]

• This method returns the status of child jobs for each run.
• Needs to be moved from tasks.py to ToilSubmitter, because Nextflow and Toil Submitter will have different ways of retrieving child jobs.
• Separate creating/updating CommandLineToolJob into separate method
• Test performances to ensure this method doesn’t introduce performance issues
• Explore the option of checking the status of child jobs together with leader job
• Consider distributing job to multiple workers
• Making sure this method is not invoked multiple times in a row, similar to what is happening to check_status_of_jobs