For server-side copy we adjusted one method DeleteObjectExactVersion.
Other deletion methods won't be used directly in code at the moment.
We will adjust other methods later or decide if we will need them at
all.
To handle deletion of objects with copies or just copies correctly we
need to use DeleteObjectExactVersion method in two places while:
* removing object before upload
* explicit object deletion
This change is also changing DeleteObjectExactVersion method to
delete pending objects because we need this functionality to
delete object before new upload.
https://github.com/storj/storj/issues/4481
Change-Id: Ieff5cc95732bb70ed8cc0ecdd62e03c929857c02
35efb6462c