autotest: allow other prearm failures while waiting for estop prearm

accels inconsistent was popping up in here.

We can ignore that - we only care we won't arm because of the estop being active.  This will also save a bit of time with the removal of the raw delay-for-10-seconds

Tools/autotest/rover.py

@@ -6071,8 +6071,9 @@ Brakes have negligible effect (with=%0.2fm without=%0.2fm delta=%0.2fm)
         })
         self.set_rc(9, 2000)
         self.reboot_sitl()
-        self.delay_sim_time(10)
-        self.assert_prearm_failure("Motors Emergency Stopped")
+        self.assert_prearm_failure(
+            "Motors Emergency Stopped",
+            other_prearm_failures_fatal=False)
         self.context_pop()
         self.reboot_sitl()