[roll] Roll zircon af8fd61..3d0feaa (3 commits)

3d0feaa [minfs] Improve encapsulation of Vnode lookup table locking
27cb10e [minfs] Decouple bitmap allocator from Minfs
c5bc41f [minfs] Avoid unnecessary inode map lookup

Change-Id: I48206612572a26499153c529d172260af0bf39ab
1 file changed