bdd tests: Make sure initial about:blank check is redone on restart

When we did "Given I have a fresh instance", we immediately did run the commands
without waiting for the initial about:blank load again.

With Qt 5.10, this causes issues as the loadFinished signal is emitted with
about:blank then, and not the real URL.

See #3003

tests/end2end/fixtures/quteprocess.py

@@ -318,6 +318,8 @@ class QuteProc(testprocess.Process):
         else:
             raise ValueError("Invalid value {!r} for 'what'.".format(what))
         if self._load_ready and self._focus_ready:
+            self._load_ready = False
+            self._focus_ready = False
             self.ready.emit()
 
     def _process_line(self, log_line):