functionObjects::timeControl: Updated to use beginTime

for consistency with the handling of restarts in Time.  See

commit 7aca9bfa78
Author: Henry Weller <http://cfd.direct>
Date:   Fri Dec 11 13:37:16 2020 +0000

    Time: Added beginTime used to rationalise the write times when restarting

    Now if a case is restarted from an arbitrary time, for example one generated at
    a premature stop condition, or with an increased writeInterval, the subsequent
    time directories written are referenced to the original start time of the case
    rather than the restart time.

src/OpenFOAM/db/functionObjects/timeControl/timeControl.C

@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2011-2019 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2011-2021 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -168,7 +168,7 @@ bool Foam::timeControl::execute()
             label executionIndex = label
             (
                 (
-                    (time_.value() - time_.startTime().value())
+                    (time_.value() - time_.beginTime().value())
                   + 0.5*time_.deltaTValue()
                 )
                /interval_

src/OpenFOAM/db/functionObjects/timeControl/timeControlFunctionObject.C

@@ -165,7 +165,7 @@ Foam::scalar Foam::functionObjects::timeControl::timeToNextWrite()
             (
                 0.0,
                 (writeTimeIndex + 1)*writeInterval
-              - (time_.value() - time_.startTime().value())
+              - (time_.value() - time_.beginTime().value())
             );
     }