test: Always wait until ssh key is added
test: Always wait until ssh key is added

In all cases except one test waited for key to be added after calling `load_key()`.
In this one case therefore every now and then happened that host shown
as 'Not connected' as in the time when tests switched to this host key was
not yet present.

So instead of fixing this one forgotten case I am moving this waiting
directly into `load_key()`.

cockpit-project/cockpit,mvollmer/cockpit,mvollmer/cockpit,mvollmer/cockpit,mvollmer/cockpit,garrett/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,garrett/cockpit,martinpitt/cockpit,garrett/cockpit,cockpit-project/cockpit,martinpitt/cockpit,garrett/cockpit,cockpit-project/cockpit,martinpitt/cockpit,garrett/cockpit,martinpitt/cockpit,cockpit-project/cockpit