revert "revert 'DexOpt anything on /system in /cache/dalvik-cache'"

Change-Id: Id41d37047f2fcb90d513ac091dfcb85492473689

Allow property to disable dexopt on /cache

Change-Id: Ic74707c4bead387bbf82e4c6d5037efc2d2ebeaf (reverse-merged from commit d927daac66e833cac73d110d525f0b27031d4c52) (reverse-merged from commit 746a36ef6452f895fbc809378a69794dcfbff874)