Disable multithreaded dexopt by default

* There is still a race condition here.
* Power users can re-enable this by setting
  persist.sys.dalvik.multithread to true

Change-Id: I03686bafbac1859695466fcb522bc5436ec82e0d

Conflicts:

	config/common.mk

Change-Id: I15fb4eb8dbe4cc09d77d3d80f0f20e250a1fb9cd
Merge "Disable multithreaded dexopt by default" into kitkat