Allow Zygote and Installd to remount directories in /data/data

Zygote/Installd now can do the following operations in app data directory:
- Mount on it
- Create directories in it
- Mount directory for each app data, and get/set attributes

Bug: 143937733
Test: No denials at boot
Test: No denials seen when creating mounts
Change-Id: I6e852a5f5182f1abcb3136a3b23ccea69c3328db
diff --git a/private/file_contexts b/private/file_contexts
index c8d9327..80f7f75 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -24,6 +24,7 @@
 /lost\+found        u:object_r:rootfs:s0
 /acct               u:object_r:cgroup:s0
 /config             u:object_r:rootfs:s0
+/data_mirror        u:object_r:mirror_data_file:s0
 /debug_ramdisk      u:object_r:tmpfs:s0
 /mnt                u:object_r:tmpfs:s0
 /postinstall        u:object_r:postinstall_mnt_dir:s0