Using sys.exit(main()) instead of main()

TrivialFix: Similar [1] in Kolla project
As we known, Exceptions are raised by the sys.exit() function. When they
are not handled, no stack traceback is printed in the Python interpreter.
Therefore, when using sys.exit(main()) instead of main()
may be more readable and reasonable.

[1] https://review.openstack.org/#/c/349353/

Change-Id: Ied52a7631da82a72f0dcf2fc9ed81840d24041d9

contrib/ipaextractor.py

@@ -362,4 +362,4 @@ def main():
                                           pprint.pformat(resp.json())))
 
 if __name__ == '__main__':
-    main()
+    sys.exit(main())

contrib/zoneextractor.py

@@ -208,4 +208,4 @@ def main():
         LOG.error(e)
 
 if __name__ == '__main__':
-    main()
+    sys.exit(main())

devstack/networking_test.py

@@ -46,6 +46,7 @@ import os
 import random
 import string
 import time
+import sys
 
 import dns
 import dns.resolver
@@ -660,4 +661,4 @@ def main():
 
 
 if __name__ == '__main__':
-    main()
+    sys.exit(main())

devstack/statsd_mock_server.py

@@ -19,6 +19,7 @@ Log to stdout or to a file.
 """
 
 from argparse import ArgumentParser
+import sys
 from time import gmtime
 from time import strftime
 import SocketServer
@@ -57,4 +58,4 @@ def main():
     server.serve_forever()
 
 if __name__ == "__main__":
-    main()
+    sys.exit(main())

tools/pretty_flake8.py

@@ -88,4 +88,4 @@ def format_dict(raw):
     return output
 
 if __name__ == '__main__':
-    main()
+    sys.exit(main())