Fix regression in PFD#fromData

Don't rely on the GC to clean up FD resources when they can
just be cleaned up immediately. We know the MemoryFile isn't
going to be used any further, so just close it.

Bug: 138323667
Test: Repro steps in bug. Verified addresses FD leak in system_server from repeatedly opening & closing settings.
Change-Id: Ic82006c9cb48f580aaad942c4679e774186382c9