Update CTurbSSTSolver.cpp to fix bug on calculating MuT #8338

Job	Run time
Build SU2 (BaseMPI)	13m 22s
Build SU2 (asan) (BaseNoMPI-asan)	16m 9s
Build SU2 (ReverseMPI)	14m 22s
Build SU2 (asan) (ReverseNoMPI-asan)	44m 26s
Build SU2 (ForwardMPI)	11m 11s
Build SU2 (BaseNoMPI)	8m 20s
Build SU2 (ReverseNoMPI)	12m 38s
Build SU2 (tsan) (BaseOMP-tsan)	12m 34s
Build SU2 (ForwardNoMPI)	10m 1s
Build SU2 (tsan) (ReverseOMP-tsan)	27m 25s
Build SU2 (BaseOMP)	7m 51s
Build SU2 (ReverseOMP)	15m 3s
Build SU2 (ForwardOMP)	10m 57s
Unit Tests (test_driver)	1m 27s
Regression Tests (vandv.py)	2m 9s
Unit Tests (test_driver_AD)	1m 26s
Regression Tests (tutorials.py)	7m 52s
Unit Tests (test_driver_DD)	52s
Regression Tests (parallel_regression.py)	13m 44s
Regression Tests (parallel_regression_AD.py)	9m 4s
Regression Tests (serial_regression.py)	16m 0s
Regression Tests (serial_regression_AD.py)	5m 17s
Regression Tests (hybrid_regression.py)	11m 4s
Regression Tests (hybrid_regression_AD.py)	3m 17s
Thread Sanitizer Tests (hybrid_regression.py)	26m 40s
Thread Sanitizer Tests (hybrid_regression_AD.py)	11m 22s
Address Sanitizer Tests (serial_regression.py)	15m 36s
Address Sanitizer Tests (serial_regression_AD.py)	5m 58s
	5h 36m 7s

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