catchunks: increase retx limit and improve statistics

Increased the retx limit from 3 to 15 (default in Linux TCP).
Added statistics about skipped retransmission.
Cleaned up statistic output.

Change-Id: I66ce9ac9fa08f7492f84bec48b7464ddb1228ab1
refs: #4861 #4603
diff --git a/tests/chunks/discover-version-fixture.hpp b/tests/chunks/discover-version-fixture.hpp
index ed18235..d42429a 100644
--- a/tests/chunks/discover-version-fixture.hpp
+++ b/tests/chunks/discover-version-fixture.hpp
@@ -75,7 +75,7 @@
     Options options;
     options.isVerbose = false;
     options.interestLifetime = time::seconds(1);
-    options.maxRetriesOnTimeoutOrNack = 3;
+    options.maxRetriesOnTimeoutOrNack = 15;
     return options;
   }