Supply librarySearchPath to PathClassLoader

PathClassLoader needs librarySearchPath in order to
be able to find native libraries.

The java.library.path property is no longer implicitly
applied to all basedexclassloaders, and needs to be
passed explicitly.

Bug: http://b/28449304
Change-Id: Id5b4273553d783c0f7a964f72ecb2c99f3aeaf6f
(cherry picked from commit 3a79b638)