Manually unmount /data_mirror mounts in the right order

Test: atest CtsUserspaceRebootHostSideTestCases
Bug: 152823078
Change-Id: I57ff9182807630d8cbcf3ca6374fdd6dc6379da5
diff --git a/rootdir/init.rc b/rootdir/init.rc
index adfdb7b..6564e8f 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -1063,6 +1063,12 @@
   start vold
   exec - system system -- /system/bin/vdc checkpoint resetCheckpoint
   exec - system system -- /system/bin/vdc checkpoint markBootAttempt
+  # Unmount /data_mirror mounts in the reverse order of corresponding mounts.
+  umount /data_mirror/data_ce/null/0
+  umount /data_mirror/data_ce/null
+  umount /data_mirror/data_de/null
+  umount /data_mirror/cur_profiles
+  umount /data_mirror
   remount_userdata
   start bootanim