[net] Cleanup maxuploadtarget

* log: nMaxOutboundLimit is in bytes
* log: Hide misleading -maxuploadtarget=0 warning
* qa : Minor cleanup to maxuploadtarget rpc tests
* net: Use DEFAULT_MAX_UPLOAD_TARGET = 0

src/net.h

@@ -60,6 +60,8 @@ static const bool DEFAULT_UPNP = false;
 static const size_t MAPASKFOR_MAX_SZ = MAX_INV_SZ;
 /** The maximum number of peer connections to maintain. */
 static const unsigned int DEFAULT_MAX_PEER_CONNECTIONS = 125;
+/** The default for -maxuploadtarget. 0 = Unlimited */
+static const uint64_t DEFAULT_MAX_UPLOAD_TARGET = 0;
 
 unsigned int ReceiveFloodSize();
 unsigned int SendBufferSize();