Fixed activation_key tests and user tests

- Blocked delete_user tests with bzid as UI doesn't raise success notification on deletion
- Updated the length of first_name to 10 instead of 50
- Blocked two negative test where we update description with more than 1000 char
- Search for updated entity doesn't work so blocked `test_positive_update_activation_key_1` with bzid
- Converted `create_cv` function in three diff functions as  create_cv fn doesn't create new manifest when a test calls it. I think it uses the same object again and again and tried to import same manifest,  so test were failing with error:
: [u'Import is the same as existing data\nOwner has already imported from another subscription management application.']

So I'm calling manifest clone and upload explicitly in the appropriate test itself rather than from a common function.