Move system default values in system partition

The following properties are specified under platform/build as system
default values.

- tombstoned.max_tombstone_count
- debug.atrace.tags.enableflags
- dalvik.vm.dex2oat-minidebuginfo

So they should move into system partition.

Bug: 64661857
Test: confirmed that the default properties were stored in
/system/etc/prop.default on sailfish device
Change-Id: Ic34c05fd9761e281962b6bb425e4babedfca45a9