Only move private attrs when building framework

When aapt was changed to move private attributes into a different type
(9b624c18), attributes only were moved
when building the framework. When this functionality was ported to
aapt2, all apps using the public tag would have their private
attributes moved. The change does not appear to be intentional and
thus is a parity issue.

This change only moves private attributes when building a package with
an id of 0x01.

Bug: 151683505
Test: manual
Change-Id: Ic9843f99e428f94cb6a55988a3881b8a91c7d7e2