Fix log presentation

Putting back-off delay at the end makes it unlikely to see it because
when there are too many scheduledInstances, log get truncated by
rsyslog. Delay is more important and having an extract of few
scheduledInstances is enough.

src/main/scala/mesosphere/marathon/core/launcher/impl/OfferProcessorImpl.scala

@@ -83,10 +83,11 @@ private[launcher] class OfferProcessorImpl(
   private def logOffer(offer: Offer): Unit = {
     val offerId = offer.getId.getValue
     val agentId = offer.getSlaveId.getValue
-    logger.debug(s"Processing offer: offerId $offerId, agentId $agentId")
+    logger.info(s"Processing offer: offerId $offerId, agentId $agentId (${offer.getHostname})")
     logger.debug(offer.toString)
   }
 
+  // This is likely beginning of offer matching
   override def processOffer(offer: Offer): Future[Done] = {
     incomingOffersMetric.increment()
     logOffer(offer)

src/main/scala/mesosphere/marathon/core/launchqueue/impl/TaskLauncherActor.scala

@@ -346,7 +346,7 @@ private class TaskLauncherActor(
   private[this] def launchAllowed(now: Timestamp, configRef: RunSpecConfigRef): Boolean = launchAllowedAt.get(configRef).exists(_ <= now)
   private[this] def shouldLaunchInstances(now: Timestamp): Boolean = {
     if (scheduledInstances.nonEmpty || launchAllowedAt.nonEmpty)
-      logger.info(s"Found scheduled instances: ${scheduledInstances.map(_.instanceId).mkString(",")} and current back-off map: $launchAllowedAt")
+      logger.info(s"Found scheduled instances (current back-off map $launchAllowedAt): ${scheduledInstances.map(_.instanceId).mkString(",")}")
     scheduledInstances.nonEmpty && scheduledVersions.exists { configRef => launchAllowed(now, configRef) }
   }