Removed mkdir_p by adding "--create-dir" flag to curl.
Removed mkdir_p by adding "--create-dir" flag to curl.

Fixed bug that popped up in AWSjobStore tests where parallel targets
would be executing "updateGlobalFile" on the same file causing conflict
errors.  Nodes that spawn parallel targets that may update the same file
concurrently are now responsible for downloading and updating the files
before the children are created. 

Removed "target_teardown" as script now checks for file's existence
before downloading.
BD2KGenomics/toil-scripts,jpfeil/toil-scripts,BD2KGenomics/toil-scripts,jpfeil/toil-scripts,fnothaft/toil-scripts,fnothaft/toil-scripts