TestObjectController refactoring

From the related change of ECDuplication, Swift have a couple of Test
classes for EC policy, normal EC and EC Duplication, in the
test/unit/proxy/test_server.py. To enable the classes, the related change
abstracts the EC test cases as the ECTestMixin class to gather test
methods into one place but it was worse because TestObjectController did
still have both test cases for replication and for ec that may be hard
to understand the test class structure.

Hence, this patch attempts to refactor the structure as

From:

     ECTestMixin
            |
    -------------------------------------
    |                                   |
TestObjectController           TestObjectControllerECDuplication
(for replication and EC)       (for EC Duplication Policy)

To:

    BaseTestObjectController
            |
    --------------------------------------
    |                                    |
TestReplicatedObjectController  BaseTestECObjectController
(for replication)                        |
                          ---------------------------------
                          |                               |
                TestECObjectController    TestECDuplicationObjectController
                (for EC policy)           (for EC Duplication Policy)

Some more cleanups are in follow up patches because this patch shows a lot
of moving code chunks which could be hard to compare the diff. To make
the review easy, this patch forcus on ONLY the structure changes as
possible.

Related-Change: Idd155401982a2c48110c30b480966a863f6bd305
Related-Change: I25a3f8fc837706d78dca226fe282d9e5ead65a0d
Change-Id: Ifd3d0fa66773e640bb61cc528f7a1b2358e97d91

test/unit/proxy/test_mem_server.py

@@ -33,7 +33,8 @@ class TestProxyServer(test_server.TestProxyServer):
     pass
 
 
-class TestObjectController(test_server.TestObjectController):
+class TestReplicatedObjectController(
+        test_server.TestReplicatedObjectController):
     def test_PUT_no_etag_fallocate(self):
         # mem server doesn't call fallocate(), believe it or not
         pass
@@ -42,6 +43,8 @@ class TestObjectController(test_server.TestObjectController):
     def test_policy_IO(self):
         pass
 
+
+class TestECObjectController(test_server.TestECObjectController):
     def test_PUT_ec(self):
         pass