Allow mode of TileService to be changed

Since the mode of a tile service was set in onTileAdded, it couldn't
be controlled by developers if they updated their tile.  To handle
the mode has been moved to a boolean meta-data flag to indicate
a tile should be an active tile.

Bug: 28043969
Change-Id: I6403d34f8cb70809edc07769389d5a1f835c1ab3