Timing failures from unmatched Pacer::start in Tendencies::computeTracerTendenciesOnly #583

Description

Changes merged in #447 leave an open Pacer timer for Tend:tracerHorzAdv on line 987 of Tendencies.cpp:

This results in:

• an unmatched open timer when FCT == true;
• two starts and only one stop when FCT == false.

Impact

Running omega_run.sh with a clean build from the current develop branch using the default yaml results in the following:

• An error message is printed to terminal: 0: newchild: child Omega:Stepper:doStep can't be a parent of itself
• The following warning is written to the end of omega.log:

[WARNING] Pacer: Following 12 timer(s) is/are still open.
        RunLoop
        Stepper:firstDoStep
        Stepper:doStep
        Stepper:doStep
        Stepper:doStep
        Stepper:doStep
        Stepper:doStep
        Stepper:doStep
        Stepper:doStep
        Stepper:doStep
        Stepper:doStep
        Stepper:doStep

• The timer hierarchy gets corrupted and only the following timers from the run loop are written to omega.timing.0:

  "Omega:RunLoop"                                                -       1    -       0.716626     0.716626     0.716626         0.000000
    "Omega:Stepper:firstDoStep"                                  -       1    -       0.060676     0.060676     0.060676         0.000000
    "Omega:Finalize"                                             -       1    -       0.000431     0.000431     0.000431         0.000000

Confirmed similar behavior on Chrysalis with intel, pm-cpu with intel, and Frontier with craygnu

Proposed fix

Remove the duplicate start from the non-FCT branch and move the stop outside the FCT/non-FCT branch.