Relax namespace restriction on system server classloader

Add java.library.path to list of permitted paths
for system server classloader. This allows libraries
loaded in system server classloader namespace to
dlopen libraries under /system/lib/somedir

Test: m
Bug: http://b/31652397
Change-Id: Ief70aaa81cde4983c8de1e07b4ef23e1fadf35a0