Adds "message Checksum" to TapeFileLsItem

eos_cta/protobuf/cta_admin.proto

@@ -459,6 +459,7 @@ message TapeLsItem {
 }
 
 message TapeFileLsItem {
+  message Checksum {
     common.ChecksumBlob.Checksum.Type type  = 1;       //< Checksum type
     string value                            = 2;       //< Checksum value, differs from cta.common.ChecksumBlob.Checksum.value
                                                        //< in that value is a decoded string not a byte array