Add initial reinit_func(1.) call in Euler2Solver

We need the call to reinit_func to set the time, t, in the context
to the correct value. Also added clarifying comments in EulerSolver
and Euler2Solver that we're also setting the time in addition to
possibly resetting the mesh if there's mesh motion.

There is probably a way to make this more efficient such that we
only call reinit_func twice in Euler2Solver, but I didn't put any
thought into it.

src/solvers/euler2_solver.C

@@ -134,6 +134,9 @@ bool Euler2Solver::_general_residual (bool request_jacobian,
   context.get_elem_solution_rate() *=
     context.elem_solution_rate_derivative;
 
+  // Move the mesh into place first if necessary, set t = t_{n+1}
+  (context.*reinit_func)(1.);
+
   // First, evaluate time derivative at the new timestep.
   // The element should already be in the proper place
   // even for a moving mesh problem.
@@ -167,7 +170,7 @@ bool Euler2Solver::_general_residual (bool request_jacobian,
   context.get_elem_solution().swap(old_elem_solution);
   context.elem_solution_derivative = 0.0;
 
-  // Move the mesh into place first if necessary
+  // Move the mesh into place if necessary, set t = t_{n}
   (context.*reinit_func)(0.);
 
   jacobian_computed =
@@ -194,7 +197,7 @@ bool Euler2Solver::_general_residual (bool request_jacobian,
   context.get_elem_solution().swap(old_elem_solution);
   context.elem_solution_derivative = 1;
 
-  // Restore the elem position if necessary
+  // Restore the elem position if necessary, set t = t_{n+1}
   (context.*reinit_func)(1.);
 
   // Add back (or restore) the old residual/jacobian

src/solvers/euler_solver.C

@@ -129,7 +129,7 @@ bool EulerSolver::_general_residual (bool request_jacobian,
   // Move theta_->elem_, elem_->theta_
   context.get_elem_solution().swap(theta_solution);
 
-  // Move the mesh into place first if necessary
+  // Move the mesh into place first if necessary, set t = t_{\theta}
   (context.*reinit_func)(theta);
 
   // Get the time derivative at t_theta
@@ -139,7 +139,7 @@ bool EulerSolver::_general_residual (bool request_jacobian,
   jacobian_computed = (_system.*mass)(jacobian_computed, context) &&
     jacobian_computed;
 
-  // Restore the elem position if necessary
+  // Restore the elem position if necessary, set t = t_{n+1}
   (context.*reinit_func)(1);
 
   // Move elem_->elem_, theta_->theta_