Make ConsoleStream thread-safe

Use the same mutex for both `operator<<` overloads. Refs CIVET
failure https://civet.inl.gov/job/2295949/ on libMesh/libmesh#3883

framework/include/outputs/ConsoleStream.h

@@ -96,9 +96,10 @@ class ConsoleStream
   /// of something in AutomaticMortarGeneration that requires
   /// this to be trivially copyable.
   mutable std::shared_ptr<std::ostringstream> _oss;
-};
 
-extern std::mutex _stream_mutex;
+  /// Mutex to prevent concurrent read/writes, write/writes
+  static std::mutex _stream_mutex;
+};
 
 template <typename StreamType>
 const ConsoleStream &

framework/src/outputs/ConsoleStream.C

@@ -12,19 +12,17 @@
 #include "MooseUtils.h"
 #include "OutputWarehouse.h"
 
-std::mutex _stream_mutex;
+std::mutex ConsoleStream::_stream_mutex;
 
 ConsoleStream::ConsoleStream(OutputWarehouse & output_warehouse)
   : _output_warehouse(output_warehouse), _oss(std::make_shared<std::ostringstream>())
 {
 }
 
-static std::mutex manip_mutex;
-
 const ConsoleStream &
 ConsoleStream::operator<<(const StandardEndLine & manip) const
 {
-  const std::lock_guard<std::mutex> lock(manip_mutex);
+  const std::lock_guard<std::mutex> lock(_stream_mutex);
 
   if (manip == (std::basic_ostream<char> & (*)(std::basic_ostream<char> &)) & std::endl)
     (*_oss) << '\n';