Use __init__ == '__main__' pattern in script

Use the typical __init__ == '__main__' pattern to determine if the code
is being run as a script, and only execute the main code if true. This
makes the code more portable to other projects.
Signed-off-by: Grant Likely <grant.likely@arm.com>

parser.py

@@ -578,7 +578,7 @@ def combine_dbs(db1, db2):
     return cross_check
 
 
-def main():
+if __name__ == '__main__':
     parser = argparse.ArgumentParser(
         description='Process SCT results.'
                     ' This program takes the SCT summary and sequence files,'
@@ -751,6 +751,3 @@ def main():
             print(
                 x["guid"], ":", x["name"], "with", args.find_key, ":",
                 x[args.find_key])
-
-
-main()