Fix for driver disconnect bug

    * Fix in remotemininetdriver which caused an exception
    * Modify teston.py to print exceptions encountered in disconnect
    * Fix Typo in mininet driver and modify log messages
    * Add return values to the disconnect functions
    * some code cleanup in teston.py
diff --git a/TestON/drivers/common/cli/onosdriver.py b/TestON/drivers/common/cli/onosdriver.py
index bc71a7f..c2b3693 100644
--- a/TestON/drivers/common/cli/onosdriver.py
+++ b/TestON/drivers/common/cli/onosdriver.py
@@ -79,7 +79,7 @@
         """
         Called when Test is complete to disconnect the ONOS handle.
         """
-        response = ''
+        response = main.TRUE
         try:
             self.handle.sendline( "" )
             self.handle.expect( "\$" )