Allow access to the metadata partition for metadata encryption.

Bug: 63927601
Test: Enable metadata encryption in fstab on Taimen, check boot success.
Change-Id: Id425c47d48f413d6ea44ed170835a52d0af39f9f

private/e2fs.te

+allow e2fs devpts:chr_file { read write };
+allow e2fs metadata_block_device:blk_file rw_file_perms;
+

private/fsck.te

 typeattribute fsck coredomain;
 
 init_daemon_domain(fsck)
+
+allow fsck metadata_block_device:blk_file rw_file_perms;

public/domain.te

@@ -556,8 +556,14 @@ neverallow {
 # The metadata block device is set aside for device encryption and
 # verified boot metadata. It may be reset at will and should not
 # be used by other domains.
-neverallow { domain -init -recovery -vold } metadata_block_device:blk_file
-  { append link rename write open read ioctl lock };
+neverallow {
+  domain
+  -init
+  -recovery
+  -vold
+  -e2fs
+  -fsck
+} metadata_block_device:blk_file { append link rename write open read ioctl lock };
 
 # No domain other than recovery and update_engine can write to system partition(s).
 neverallow { domain -recovery -update_engine } system_block_device:blk_file { write append };

public/fsck.te

@@ -44,7 +44,6 @@ allow fsck rootfs:dir r_dir_perms;
 neverallow fsck {
   boot_block_device
   frp_block_device
-  metadata_block_device
   recovery_block_device
   root_block_device
   swap_block_device