Allow installd to dexopt apps on expanded storage.

avc: denied { search } for name="expand" dev="tmpfs" ino=3130 scontext=u:r:installd:s0 tcontext=u:object_r:mnt_expand_file:s0 tclass=dir permissive=0

Bug: 19993667
Change-Id: Ie53df62aa79ae14cd56d7c6f2429b4be382164d1