BUG: Wrong First extrapolated value of the merit function (fixes #1948)

Affected only the first optimisation cycle, if line search was enabled

If eta was not set explicitly, it was computed after evaluating the
directional derivative of the merit function, which was computed
wrongly, leading to an erroneous value of the extrapolated merit
function value.

src/optimisation/adjointOptimisation/adjoint/optimisation/optimisationType/incompressible/optimisationType/optimisationTypeIncompressible.C

@@ -175,9 +175,6 @@ void optimisationType::update()
 
 void optimisationType::update(scalarField& direction)
 {
-    // Compute eta if needed
-    computeEta(direction);
-
     // Multiply with line search step, if necessary
     scalarField correction(direction);
     if (lineSearch_.valid())
@@ -218,6 +215,9 @@ tmp<scalarField> optimisationType::computeDirection()
     scalarField& correction = tcorrection.ref();
     correction = updateMethod_->returnCorrection();
 
+    // Compute eta if needed
+    computeEta(correction);
+
     return tcorrection;
 }