Properly restore iostream format flags

std::setiosflags only enables additional flags, but we might have to
disable some when restoring the original state. std::ios_base::flags
does what we need.

dune/solvers/solvers/loopsolver.cc

@@ -151,8 +151,8 @@ void ::LoopSolver<VectorType, BitVectorType>::solve()
                 std::cout << std::fixed
                           << std::setw(9) << std::setprecision(5) << convRate;
 
-            std::cout << std::setprecision(oldPrecision)
-                      << std::setiosflags(oldFormatFlags);
+            std::cout << std::setprecision(oldPrecision);
+            std::cout.flags(oldFormatFlags);
 
             std::cout << this->iterationStep_->getOutput();
             std::cout << std::endl;