[CLC-3478] Include P/NP option in the grades drop down of GPA calculator
Merge pull request #2307 from haroonrasheed333/CLC-3478

[CLC-3478] Include P/NP option in the grades drop down of GPA calculator
Users who can act-as should be able to act-as any user

https://jira.ets.berkeley.edu/jira/browse/CLC-3419

Reproduced the error:
Made an integration test that fails in order to reproduce the bug:
"make sure admin users can act as a user who has never signed in before"
even in production
Thanks for your help, Chris!

The fix:
Removed a block of code from the SessionsController that didn't allow
viewing of users that had never logged in production.
Users who can act-as should be able to act-as any user
https://jira.ets.berkeley.edu/jira/browse/CLC-3419

Asserting that the superuser can_act_as is redundant.
Removed line from test
Users who can act-as should be able to act-as any user
https://jira.ets.berkeley.edu/jira/browse/CLC-3419

Use a random ID instead of 2040. Depending on test execution order, another test may have logged in as 2040 before this test runs, causing a spurious test failure.

@random_id = Time.now.to_f.to_s.gsub(".", "")