libsnapshot: Fix DataWipeRollbackInRecovery test

HandleImminentDataWipe left /metadata unmounted in recovery.
Test: run it

Change-Id: Ifc76203e46cf5e783d4badf7f8e3e8d0b78eaeb0
diff --git a/fs_mgr/libsnapshot/snapshot_test.cpp b/fs_mgr/libsnapshot/snapshot_test.cpp
index d7c69a6..12bf399 100644
--- a/fs_mgr/libsnapshot/snapshot_test.cpp
+++ b/fs_mgr/libsnapshot/snapshot_test.cpp
@@ -1284,6 +1284,8 @@
     auto new_sm = SnapshotManager::NewForFirstStageMount(test_device);
 
     ASSERT_TRUE(new_sm->HandleImminentDataWipe());
+    // Manually mount metadata so that we can call GetUpdateState() below.
+    MountMetadata();
     EXPECT_EQ(new_sm->GetUpdateState(), UpdateState::Unverified);
     EXPECT_TRUE(test_device->IsSlotUnbootable(1));
     EXPECT_FALSE(test_device->IsSlotUnbootable(0));