Give vold permission to wipe a block device

During mountFstab call, vold might need to wipe and re-format a device.
See code in system/vold/model/PublicVolume.cpp , PublicVolume::doFormat
Allow IOCTLs such as BLKDISCARDZEROES for wiping.

Test: th
Bug: 279808236
Change-Id: I0bebf850aa45ece6227fa5c3e9c3fdb38164f79e
diff --git a/private/vold.te b/private/vold.te
index 957e5d0..4256ac3 100644
--- a/private/vold.te
+++ b/private/vold.te
@@ -7,6 +7,10 @@
 domain_auto_trans(vold, sdcardd_exec, sdcardd);
 domain_auto_trans(vold, fuseblkd_untrusted_exec, fuseblkd_untrusted);
 
+# Switch to e2fs domain when running mkfs.ext4 to format a partition
+domain_auto_trans(vold, e2fs_exec, e2fs);
+
+
 # For a handful of probing tools, we choose an even more restrictive
 # domain when working with untrusted block devices
 domain_trans(vold, blkid_exec, blkid);