Tools: expect message for EKF readiness rather than sleeping

This solves a problem for me when running Valgrind as
30s was not sufficient

Tools/autotest/apmrover2.py

@@ -18,9 +18,12 @@ HOME = mavutil.location(40.071374969556928, -105.22978898137808, 1583.702759, 24
 homeloc = None
 
 
-def arm_rover(mavproxy, mav):
+def wait_ready_to_arm(mavproxy):
     # wait for EKF and GPS checks to pass
-    wait_seconds(mav, 30)
+    mavproxy.expect('IMU0 is using GPS')
+
+def arm_rover(mavproxy, mav):
+    wait_ready_to_arm(mavproxy);
 
     mavproxy.send('arm throttle\n')
     mavproxy.expect('ARMED')

Tools/autotest/arducopter.py

@@ -29,6 +29,10 @@ num_wp = 0
 speedup_default = 10
 
 
+def wait_ready_to_arm(mavproxy):
+    # wait for EKF and GPS checks to pass
+    mavproxy.expect('IMU0 is using GPS')
+
 def hover(mavproxy, mav, hover_throttle=1500):
     mavproxy.send('rc 3 %u\n' % hover_throttle)
     return True
@@ -1027,8 +1031,7 @@ def fly_ArduCopter(binary, viewerip=None, use_map=False, valgrind=False, gdb=Fal
         setup_rc(mavproxy)
         homeloc = mav.location()
 
-        # wait for EKF and GPS checks to pass
-        wait_seconds(mav, 30)
+        wait_ready_to_arm(mavproxy)
 
         # Arm
         print("# Arm motors")
@@ -1378,8 +1381,7 @@ def fly_CopterAVC(binary, viewerip=None, use_map=False, valgrind=False, gdb=Fals
         print("Lowering rotor speed")
         mavproxy.send('rc 8 1000\n')
 
-        # wait for EKF and GPS checks to pass
-        wait_seconds(mav, 30)
+        wait_ready_to_arm(mavproxy)
 
         # Arm
         print("# Arm motors")

Tools/autotest/arduplane.py

@@ -19,12 +19,14 @@ WIND = "0,180,0.2"  # speed,direction,variance
 
 homeloc = None
 
+def wait_ready_to_arm(mavproxy):
+    # wait for EKF and GPS checks to pass
+    mavproxy.expect('IMU0 is using GPS')
 
 def takeoff(mavproxy, mav):
     """Takeoff get to 30m altitude."""
 
-    # wait for EKF and GPS checks to pass
-    wait_seconds(mav, 30)
+    wait_ready_to_arm(mavproxy)
 
     mavproxy.send('arm throttle\n')
     mavproxy.expect('ARMED')