ari: Add events for playback and recording.

While there were events defined for playback and recording
these were not actually sent. This change implements the
to_json handlers which produces them.

(closes issue ASTERISK-22710)
Reported by: Jonathan Rose

Review: https://reviewboard.asterisk.org/r/3026/
........

Merged revisions 403119 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@403120 65c4cc65-6c06-0410-ace0-fbb531ad65f3

rest-api/api-docs/events.json

@@ -153,11 +153,6 @@
 					"type": "LiveRecording",
 					"description": "Recording control object",
 					"required": true
-				},
-				"cause": {
-					"type": "string",
-					"description": "Cause for the recording failure",
-					"required": true
 				}
 			}
 		},

rest-api/api-docs/recordings.json

@@ -307,6 +307,11 @@
 						]
 					}
 				},
+				"cause": {
+					"required": false,
+					"type": "string",
+					"description": "Cause for recording failure if failed"
+				},
 				"state": {
 					"required": true,
 					"type": "string"