TranformFstabForDsu adds missing partition entries to fstab

Fix odd bug that TranformFstabForDsu doesn't emplace entry to fstab.

.avb_keys should be set to "/avb", the directory that stores all DSU
avbpubkeys, instead of appending.

Bug: 165471299
Test: Boot a multipartition DSU package
Change-Id: I62ee2f8bf7113f6d2af8cc34ef19c9743029ea0a
1 file changed