Autotest: Remove frame initialisation.

This will otherwise override the --frame parameter. The init() function takes care of the initialisation

Tools/autotest/arducopter.py

@@ -1106,7 +1106,6 @@ class AutoTestCopter(AutoTest):
 
     def autotest(self):
         """Autotest ArduCopter in SITL."""
-        self.frame = '+'
         if not self.hasInit:
             self.init()
 

Tools/autotest/quadplane.py

@@ -148,7 +148,6 @@ class AutoTestQuadPlane(AutoTest):
 
     def autotest(self):
         """Autotest QuadPlane in SITL."""
-        self.frame = 'quadplane'
         if not self.hasInit:
             self.init()