Call UploadBase::cleanupTempFile before exiting

UploadBase doesn't automatically clean up it's temporary files when the
object goes out of scope or the PHP interpreter shuts down. The
developer must make sure to manually call the cleanupTempFile() method
if the upload operation was not successful.

Bug: 58299
Change-Id: I104cb58cb70ac9d80979123f4d8653b708649dc9