Pass permitted_path to the linker as is.

Now that we have the fixed list of whitelisted libraries
there is no longer need to check if java_permitted_path is nullptr.
In fact checking it prevents custom classloaders created by apps
from loading libraries using absolute path.

Bug: http://b/28659864
Change-Id: I1bfc16a573b090f70f078ecccd0e4016939a5dc0