Behat visit should be passed through $this->execute

There's a number of cases where we call $this->getSession()->visit($url) or similar and the we call steps immediately aftewards.

In some steps we then immediately try to interact with the page - for example by pressing a button. This can cause random fails if the page has not yet finished loading.

We have two options:

1. add a call to $this->wait_for_pending_js(); or
2. create a new i_visit step which call via $this->execute().

My preference is for the new step, but then there are two further options:

1. only update those cases affected; or
2. update all, even those where it isn't necessary.

Technically speaking we only need the $this->execute() where something is followed by another interaction before the end of the step, but it may be better to call the step consistently always.