Allow devices to specify certain ro. props via TARGET_UNIFIED_DEVICE

This modifies buildinfo.sh to not set model, name, description, and
fingerprint in build.prop. These can then be set via custom init
lib.
This also fixes ota_from_target_files to function without these
props being preset.

Change-Id: I945b2c38e60b207d2d0f82b34f4f230ac21b0657

Conflicts:
	core/Makefile
	tools/releasetools/ota_from_target_files

PS2: remove assert changes, we don't use it for some reason

Change-Id: I945b2c38e60b207d2d0f82b34f4f230ac21b0657
build: set data roaming always to false

NOTE: This is a temporary fix until the cause of the issue is found

some of our devices inherit this mk here and vendor slim does not overwrite it.
Thanks Kurre for pointing out

Change-Id: Ie2ef480add1ff1614fea1b986758ceb5330f0005
Merge "build: set data roaming always to false" into kk4.4
Merge remote-tracking branch 'slim/kk4.4' into ose

Conflicts:
	core/Makefile
	tools/buildinfo.sh
	tools/releasetools/ota_from_target_files