Use Mailer's AMQP config instead of SA.

Mailer was erroneously using SA's AMQP config.

cmd/expiration-mailer/main.go

@@ -234,7 +234,7 @@ func main() {
 		dbMap, err := sa.NewDbMap(c.Mailer.DBConnect)
 		cmd.FailOnError(err, "Could not connect to database")
 
-		amqpConf := c.SA.AMQP
+		amqpConf := c.Mailer.AMQP
 		sac, err := rpc.NewStorageAuthorityClient(clientName, amqpConf, stats)
 		cmd.FailOnError(err, "Failed to create SA client")
 

test/boulder-config.json

@@ -259,7 +259,15 @@
     "nagTimes": ["24h", "72h", "168h", "336h"],
     "nagCheckInterval": "24h",
     "emailTemplate": "test/example-expiration-template",
-    "debugAddr": "localhost:8008"
+    "debugAddr": "localhost:8008",
+    "amqp": {
+      "serverURLFile": "test/secrets/amqp_url",
+      "insecure": true,
+      "SA": {
+        "server": "SA.server",
+        "rpcTimeout": "15s"
+      }
+    }
   },
 
   "publisher": {