scalability_test: make scalabilityUsers valid python code

I'm not sure if this is used, but not being valid python code cause
problems with code analysis tools

scalability_test/example/scalabilityUsers.py

 # Specify user login/password used to run the tests.
 # <password> and <user_quantity> will be automatically replaced by testnode for each configuration
 
-user_tuple = tuple([('scalability_user_%i' % x, "<password>") for x in range(0, <user_quantity>)])
\ No newline at end of file
+user_tuple = tuple([('scalability_user_%i' % x, "<password>") for x in range(0, int('<user_quantity>'))])