This fixes the cases for racing uploads with the same object names.
Before we were making some bad assumptions about what would cause
an error when trying to link/rename the final object name into
the namespace, but missed the case that another upload for the
same name could be racing with this upload and causing an incorrect
error.
This also changes the order of setting metadata to prevent
accidental setting of metadata for the current upload to another
racing upload.
This also fix auth.CheckObjectAccess() when objects are removed
while this runs.
Fixes#854
Added support to enable object lock on bucket creation in posix and azure
backends.
Implemented the logic to add object legal hold and retention on object creation
in azure and posix backends.
Added the functionality for HeadObject to return object lock related headers.
Added integration tests for these features.
