Init: add OTA directory

Add /data/ota in init so that the right selinux labels are applied.

Bug: 25612095
Change-Id: I8fd093147f8e0a5c3bd1a4007a61b0b759911cf2

rootdir/init.rc

@@ -371,6 +371,8 @@ on post-fs-data
 
     # create dalvik-cache, so as to enforce our permissions
     mkdir /data/dalvik-cache 0771 root root
+    # create the A/B OTA directory, so as to enforce our permissions
+    mkdir /data/ota 0771 root root
 
     # create resource-cache and double-check the perms
     mkdir /data/resource-cache 0771 system system