add more dangling heal related tests (#13140)

also make sure that HealObject() never returns
'ObjectNotFound' or 'VersionNotFound' errors,
as those are meaningless and not useful for the
caller.

cmd/erasure-healing.go

@@ -885,6 +885,12 @@ func isObjectDangling(metaArr []FileInfo, errs []error, dataErrs []error) (valid
 
 // HealObject - heal the given object, automatically deletes the object if stale/corrupted if `remove` is true.
 func (er erasureObjects) HealObject(ctx context.Context, bucket, object, versionID string, opts madmin.HealOpts) (hr madmin.HealResultItem, err error) {
+	defer func() {
+		if isErrObjectNotFound(err) || isErrVersionNotFound(err) {
+			err = nil
+		}
+	}()
+
 	// Create context that also contains information about the object and bucket.
 	// The top level handler might not have this information.
 	reqInfo := logger.GetReqInfo(ctx)