Set uid, gid and mode options for webstats-collector tmpfs mount

If this is not set, the symlink that is created in this directory
will not be traversable by the user that runs collector.  Otherwise
this error will be seen:

non-matching-uid symlink following attempted in sticky world-writable directory

Change-Id: I8a9a0898c00a0a58cd622c5e8d9f24f2b0515b69