res_ari: Correct Location headers returned by some ARI resources

The Location headers returned by:

 * /bridges/{bridgeId}/play
 * /bridges/{bridgeId}/record
 * /channels/{channelId}/play
 * /channels/{channelId}/record

Did not have the '/ari' prefix, and in the case of the 'play' resources, were
using 'playback' instead of 'playbacks.'

Change-Id: I957c58a3a1471bf477dae7c67faa1b74fcd9241c