remove IfUnmodifiedSince from SetDataLakeFileSystemMetadataOptions (#2383)

* remove IfUnmodifiedSince from SetDataLakeFileSystemMetadataOptions

* cl

sdk/storage/azure-storage-files-datalake/CHANGELOG.md

@@ -6,6 +6,10 @@
 
 - Renamed `ContentLength` in `FlushFileResult` to `FileSize`.
 
+### Other Changes and Improvements
+
+- Removed `IfUnmodifiedSince` from access conditions of setting filesystem metadata operation.
+
 ## 12.0.0-beta.11 (2021-05-19)
 
 ### New Features

sdk/storage/azure-storage-files-datalake/inc/azure/storage/files/datalake/datalake_options.hpp

@@ -141,7 +141,14 @@ namespace Azure { namespace Storage { namespace Files { namespace DataLake {
     /**
      * Specify the access condition for the file system.
      */
-    FileSystemAccessConditions AccessConditions;
+    struct : public LeaseAccessConditions
+    {
+      /**
+       * @brief Specify this header to perform the operation only if the resource has been
+       * modified since the specified time. This timestamp will be truncated to second.
+       */
+      Azure::Nullable<Azure::DateTime> IfModifiedSince;
+    } AccessConditions;
   };
 
   /**

sdk/storage/azure-storage-files-datalake/src/datalake_file_system_client.cpp

@@ -251,9 +251,6 @@ namespace Azure { namespace Storage { namespace Files { namespace DataLake {
   {
     Blobs::SetBlobContainerMetadataOptions blobOptions;
     blobOptions.AccessConditions.IfModifiedSince = options.AccessConditions.IfModifiedSince;
-    AZURE_ASSERT_MSG(
-        !options.AccessConditions.IfUnmodifiedSince.HasValue(),
-        "This operation doesn't support If-Unmodified-Since condition");
 
     auto result = m_blobContainerClient.SetMetadata(std::move(metadata), blobOptions, context);
     Models::SetFileSystemMetadataResult ret;