We weren't checking that the request caused by clicking on the "Send
instructions" button had finished before continuing with the test.
Perhaps that's why this test has recently failed on our CI:
```
3) Emails Reset password
Failure/Error: email = open_last_email
RuntimeError:
No email has been sent!
```
We're also adding an expectation to the `login_as_manager` method and
the methods to submit proposal and investment forms to make sure that,
when these method finish, the request finishes as well.
6c055f2713