autotest: fixed SITL without ROS installed

Tools/autotest/pysim/sim_multicopter.py

@@ -2,7 +2,6 @@
 
 from multicopter import MultiCopter
 from helicopter import HeliCopter
-from iris_ros import IrisRos
 import util, time, os, sys, math
 import socket, struct
 import select, errno
@@ -139,6 +138,7 @@ fdm = fgFDM.fgFDM()
 if opts.frame == 'heli':
     a = HeliCopter(frame=opts.frame)
 elif opts.frame == 'IrisRos':
+    from iris_ros import IrisRos
     a = IrisRos()
 else:    
     a = MultiCopter(frame=opts.frame)