Enable namespaces for all target sdk versions

We previously relied on the fact that target sdk version 0
implies system_server, which is not true, target sdk version
may be set to 0 for other apps and it means 1 - the earliest
version of android. This change enables namespaces for
apps targeting all sdk version and for system_server.

Bug: http://b/27702070
Change-Id: I16fbdeb6868c7035aec71132c80c150c08ea2cc3