txLoadBalancer can become stuck in read-only mode

[tsavannah]

txLoadBalancer contains two places where an exception could potentially cause txLoadBalancer to enter read-only mode and never leave.

One place is in manager.py:checkConfigChanges between director.setReadOnly and director.setReadWrite. This section should be wrapped in a try: except block such that if an exception happens between setReadOnly and setReadWrite, read-write will always be restored.

The other place is in admin/pages.py in the function "protect". There should be a try except surronding

"result = method(self, *args, **kwds)"