Change /dalvik-cache to be owned by root.
Change /dalvik-cache to be owned by root.

Also prune the dalvik-cache during startup if we need to generate or
relocate an image.

Bug: 17000769,16875245

(cherry picked from commit 2539613be94f599c1713627f80c7398028d1a6aa)

Change-Id: I29a70215a2207bc4e0db02ab751d32a68edf4b66

treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst,treadstoneproject/artinst