Fix an issue in EAMxx with incorrect metadata in rhist file

This commit fixes an issue during restarts that occurs with
averaged type output.  The restart history file (rhist) metadata
was incorrectly setup which could lead EAMxx to reopen files that
already had the max number of snaps in them and continue to fill
them at the restart step.

Fixes #6795

Author: AaronDonahue

components/eamxx/src/share/io/scream_output_manager.cpp

@@ -494,9 +494,14 @@ void OutputManager::run(const util::TimeStamp& timestamp)
         if (filespecs.ftype==FileType::HistoryRestart) {
           // Update the date of last write and sample size
           write_timestamp (filespecs.filename,"last_write",m_output_control.last_write_ts,true);
-          scorpio::set_attribute (filespecs.filename,"GLOBAL","last_output_filename",m_output_file_specs.filename);
           scorpio::set_attribute (filespecs.filename,"GLOBAL","num_snapshots_since_last_write",m_output_control.nsamples_since_last_write);
-          scorpio::set_attribute (filespecs.filename,"GLOBAL","last_output_file_num_snaps",m_output_file_specs.storage.num_snapshots_in_file);
+	  if (m_output_file_specs.is_open) {
+              scorpio::set_attribute (filespecs.filename,"GLOBAL","last_output_file_num_snaps",m_output_file_specs.storage.num_snapshots_in_file);
+              scorpio::set_attribute (filespecs.filename,"GLOBAL","last_output_filename",m_output_file_specs.filename);
+	  } else {
+	      scorpio::set_attribute (filespecs.filename,"GLOBAL","last_output_file_num_snaps", std::numeric_limits<int>::max());
+              scorpio::set_attribute (filespecs.filename,"GLOBAL","last_output_filename","");
+	  }
         }
         // Write these in both output and rhist file. The former, b/c we need these info when we postprocess
         // output, and the latter b/c we want to make sure these params don't change across restarts