Improve linker_namespaces CTS test

This improvements helps avoid situation when some of the libraries
expected to reside in /system/lib are moved to /vendor/lib directory.

This is not allowed and the test now checks the limited list of known
libraries to make sure that they are in /system/lib

Bug: http://b/26894351
Change-Id: I4943a8ad808537b217dfcba5e242b037ca2626a6
1 file changed