[REFACTOR] DynamicPartitionControl: Add GetSuperPartitionName

fs_mgr_get_super_partition_name() should be mocked because
it is an external dependency to libfs_mgr.

In tests, deliberately make GetSuperDevice() to return "fake_super"
instead of "super" to make sure it is mocked properly.

Test: run unittests
Test: manually apply OTA

Change-Id: I0f05d99bf168b6e658052b4bd67dc1e82ab36471
diff --git a/boot_control_android_unittest.cc b/boot_control_android_unittest.cc
index 1a87547..6f02a07 100644
--- a/boot_control_android_unittest.cc
+++ b/boot_control_android_unittest.cc
@@ -73,6 +73,13 @@
           *device = GetDmDevice(partition_name_suffix);
           return true;
         }));
+
+    ON_CALL(dynamicControl(), GetSuperPartitionName(_))
+        .WillByDefault(Return(kFakeSuper));
+  }
+
+  std::string GetSuperDevice(uint32_t slot) {
+    return GetDevice(dynamicControl().GetSuperPartitionName(slot));
   }
 
   // Return the mocked HAL module.