Don't log a warning if file system doesn't support ReopenWritableFile() (#8414)

Summary:
RocksDB logs a warning if WAL truncation on DB open fails. Its possible that on some file systems, truncation is not required and they would return ```Status::NotSupported()``` for ```ReopenWritableFile```. Don't log a warning in such cases.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8414

Reviewed By: akankshamahajan15

Differential Revision: D29181738

Pulled By: anand1976

fbshipit-source-id: 6e01e9117e1e4c1d67daa4dcee7fa59d06e057a7

db/db_impl/db_impl_open.cc

@@ -1293,7 +1293,7 @@ Status DBImpl::GetLogSizeAndMaybeTruncate(uint64_t wal_number, bool truncate,
       truncate_status = last_log->Close(IOOptions(), nullptr);
     }
     // Not a critical error if fail to truncate.
-    if (!truncate_status.ok()) {
+    if (!truncate_status.ok() && !truncate_status.IsNotSupported()) {
       ROCKS_LOG_WARN(immutable_db_options_.info_log,
                      "Failed to truncate log #%" PRIu64 ": %s", wal_number,
                      truncate_status.ToString().c_str());