Task #10320: Backported CEP4 as default cluster in XML generator to 2.20

SAS/XML_generator/src/xmlgen.py

...tor/test/test_regression.in_data/xml/20150713_4C17.31.xml

...est/test_regression.in_data/xml/20150731_G46_run1_HBA.xml

...or/test/test_regression.in_data/xml/20150810_P247P244.xml

...ML_generator/test/test_regression.in_data/xml/2MASS_1.xml

.../test_regression.in_data/xml/B1834620_HBA_LB_20150817.xml

...tor/test/test_regression.in_data/xml/LC4_020_20150813.xml

...st_regression.in_data/xml/LC4_022_3C58_HBA_parameters.xml

...ion.in_data/xml/LT5_006_4C43_HBA_calSearch_parameters.xml

...st_regression.in_data/xml/MSSS_20151207_testmultipipe.xml

...enerator/test/test_regression.in_data/xml/Ticket_6923.xml

.../test/test_regression.in_data/xml/hd156279b_reference.xml

..._generator/test/test_regression.in_data/xml/lc4_019_1.xml

...ML_generator/test/test_regression.in_data/xml/test_LB.xml

...generator/test/test_regression.in_data/xml/test_input.xml

...ression.in_data/xml/test_input_long_baseline_pipeline.xml