A suspended-versioning DELETE was recorded with createDeleteMarker, which mints a
fresh real version id each time, so repeated suspended deletes piled up delete
markers instead of overwriting a single null marker as S3 specifies. Record the
suspended delete as a 'null' marker with a fixed file name (v_null) and point the
latest-version pointer at it explicitly; putSuspendedVersioningObject's existing
null-version cleanup removes it on the next suspended PUT, so the object undeletes
cleanly and at most one null marker exists. Enabled-versioning deletes are
unchanged (still distinct historical markers).
Update TestSuspendedVersioningDeleteBehavior to the AWS-correct counts: one null
marker after a suspended delete, and the null marker plus one real marker after a
re-enabled delete.