Avoid recycling recently removed user IDs.

Currently, installd doesn't correctly evict VFS cache entries for
FUSE emulated external storage.  This means zygote processes have an
inconsistent view of the FUSE daemon when the system rapidly
recycles user IDs.

To work around this, only consider recycling a user ID after its
VFS cache entries have expired.  The emulated storage FUSE daemon
currently uses a 'entry_valid' timeout of 10 seconds.

Bug: 7407902
Change-Id: Id80cbdd2215d8456467fb31e4c209ca12a505e16