Remove network state wipe from UnloadBlockIndex.

UnloadBlockIndex is only used during init if we end up reindexing
to clear our block state so that we can start over. However, at
that time no connections have been brought up as CConnman hasn't
been started yet, so all of the network processing state logic is
empty when its called.

Additionally, the initialization of the recentRejects set is moved
to InitPeerLogic.

src/init.cpp

@@ -1100,6 +1100,10 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
         return false;
 #endif
     // ********************************************************* Step 6: network initialization
+    // Note that we absolutely cannot open any actual connections
+    // until the very end ("start node") as the UTXO/block state
+    // is not yet setup and may end up being set up twice if we
+    // need to reindex later.
 
     assert(!g_connman);
     g_connman = std::unique_ptr<CConnman>(new CConnman(GetRand(std::numeric_limits<uint64_t>::max()), GetRand(std::numeric_limits<uint64_t>::max())));