[XrdSsi] Work around Metadata bug

First character of XrdSsi metadata is overwritten with zero, see
https://github.com/xrootd/xrootd/issues/537
This workaround adds a dummy character to the front of the metadata on
the server side and removes it on the client side.

frontend/TestSsiRequestProc.h

@@ -95,6 +95,9 @@ void RequestProc<RequestType, ResponseType, MetadataType, AlertType>::Execute()
 
    if(response_str.size() > 0)
    {
+      // Temporary workaround for XrdSsi bug #537:
+      response_str = " " + response_str;
+
       SetMetadata(response_str.c_str(), response_str.size());
    }
 

frontend/XrdSsiPbRequest.h

@@ -130,10 +130,12 @@ bool XrdSsiPbRequest<RequestType, ResponseType, MetadataType, AlertType>::Proces
 
          if(metadata_len > 0)
          {
+            // Temporary workaround for XrdSsi bug #537:
+            ++metadata_buffer; --metadata_len;
+
             // Deserialize the metadata
 
             const std::string metadata_str(metadata_buffer, metadata_len);
-std::cerr << "metadata_str = " << metadata_str << std::endl;
 
             MetadataType metadata;