mock tests cmake cfg: use PYTHON_DEFAULT_INTERP instead of _EXECUTABLE
mock tests cmake cfg: use PYTHON_DEFAULT_INTERP instead of _EXECUTABLE

Signed-off-by: Alex Tereschenko <c1573d8a2714f7b294fae3af1bb5e489479ca966@gmail.com>
Signed-off-by: Brendan Le Foll <3e0e8c4069934e8b47d99704927a85c66c0ceb33@intel.com>

g-vidal/mraa,malikabhi05/mraa,ncrastanaren/mraa,arfoll/mraa,KurtE/mraa,alext-mkrs/mraa,malikabhi05/mraa,sergev/mraa,ncrastanaren/mraa,Jon-ICS/mraa,Propanu/mraa,arfoll/mraa,yongli3/mraa,KurtE/mraa,sergev/mraa,g-vidal/mraa,stefan-andritoiu/mraa,stefan-andritoiu/mraa,stefan-andritoiu/mraa-gpio-chardev,stefan-andritoiu/mraa-gpio-chardev,intel-iot-devkit/mraa,jontrulson/mraa,Jon-ICS/mraa,stefan-andritoiu/mraa,intel-iot-devkit/mraa,jontrulson/mraa,sergev/mraa,KurtE/mraa,alext-mkrs/mraa,intel-iot-devkit/mraa,malikabhi05/mraa,alext-mkrs/mraa,sergev/mraa,ncrastanaren/mraa,KurtE/mraa,alext-mkrs/mraa,malikabhi05/mraa,jontrulson/mraa,stefan-andritoiu/mraa-gpio-chardev,ncrastanaren/mraa,arfoll/mraa,Propanu/mraa,arfoll/mraa,yongli3/mraa,intel-iot-devkit/mraa,yongli3/mraa,Propanu/mraa,jontrulson/mraa,g-vidal/mraa,yongli3/mraa,intel-iot-devkit/mraa,alext-mkrs/mraa,jontrulson/mraa,ncrastanaren/mraa,stefan-andritoiu/mraa,stefan-andritoiu/mraa-gpio-chardev,Propanu/mraa,malikabhi05/mraa,Jon-ICS/mraa,Propanu/mraa,yongli3/mraa,KurtE/mraa,g-vidal/mraa,g-vidal/mraa,stefan-andritoiu/mraa,arfoll/mraa,sergev/mraa,stefan-andritoiu/mraa-gpio-chardev