Made transaction.managed a no-op and deprecated it.

enter_transaction_management() was nearly always followed by managed().

In three places it wasn't, but they will all be refactored eventually.
The "forced" keyword argument avoids introducing behavior changes until
then.

This is mostly backwards-compatible, except, of course, for managed
itself. There's a minor difference in _enter_transaction_management:
the top self.transaction_state now contains the new 'managed' state
rather than the previous one. Django doesn't access
self.transaction_state in _enter_transaction_management.

django/test/testcases.py

@@ -67,7 +67,6 @@ real_commit = transaction.commit
 real_rollback = transaction.rollback
 real_enter_transaction_management = transaction.enter_transaction_management
 real_leave_transaction_management = transaction.leave_transaction_management
-real_managed = transaction.managed
 real_abort = transaction.abort
 
 def nop(*args, **kwargs):
@@ -78,7 +77,6 @@ def disable_transaction_methods():
     transaction.rollback = nop
     transaction.enter_transaction_management = nop
     transaction.leave_transaction_management = nop
-    transaction.managed = nop
     transaction.abort = nop
 
 def restore_transaction_methods():
@@ -86,7 +84,6 @@ def restore_transaction_methods():
     transaction.rollback = real_rollback
     transaction.enter_transaction_management = real_enter_transaction_management
     transaction.leave_transaction_management = real_leave_transaction_management
-    transaction.managed = real_managed
     transaction.abort = real_abort
 
 
@@ -833,7 +830,6 @@ class TestCase(TransactionTestCase):
 
         for db_name in self._databases_names():
             transaction.enter_transaction_management(using=db_name)
-            transaction.managed(True, using=db_name)
         disable_transaction_methods()
 
         from django.contrib.sites.models import Site