QA: reuse "When I have created a Flow topic"

Convert two more tests to use
  When I have created a Flow topic with title "Foo"
instead of I type ...  And I type ...  And I click New topic save

The modified tests pass for me in Firefox against beta labs.

Change-Id: Iefeac6dd7ebf9cc1b4f201967e7bc8e0bb71c0b3
Merge "QA: reuse "When I have created a Flow topic""