sap_software_download: Fix for failed checksums not correctly retrying

[marcelmamula]

Issue

Issue was detected when downloads were interrupted, which resulted in retry attempt detecting partial file and skipping it.
#39

Root cause:

• Function _download_file was not deleting partial files (failed checksum) at correct point in time
• Role detected failure because of checksum, retried running module, which detected file that was not deleted resulting in success.

Changes

• Move up deletion of file outside of retry conditional
• Remove retry parameters in role tasks

[berndfinger]

I didn't encounter the issue during my testing but the download worked as before, so:

LGTM!