Add err to solicitedAsyncTxHandler.loop log message (#3123)

## Summary

I noticed log messages like this:
```
{"file":"txHandler.go","function":"github.com/algorand/go-algorand/data.(*solicitedAsyncTxHandler).loop","level":"info","line":541,"msg":"solicitedAsyncTxHandler was unable to relay transaction message : %!v(MISSING)","time":"2021-10-20T23:18:40.220089Z"}
{"file":"txHandler.go","function":"github.com/algorand/go-algorand/data.(*solicitedAsyncTxHandler).loop","level":"info","line":541,"msg":"solicitedAsyncTxHandler was unable to relay transaction message : %!v(MISSING)","time":"2021-10-20T23:18:40.220226Z"}
{"file":"txHandler.go","function":"github.com/algorand/go-algorand/data.(*solicitedAsyncTxHandler).loop","level":"info","line":541,"msg":"solicitedAsyncTxHandler was unable to relay transaction message : %!v(MISSING)","time":"2021-10-20T23:18:40.220300Z"}
{"file":"txHandler.go","function":"github.com/algorand/go-algorand/data.(*solicitedAsyncTxHandler).loop","level":"info","line":541,"msg":"solicitedAsyncTxHandler was unable to relay transaction message : %!v(MISSING)","time":"2021-10-20T23:18:40.228731Z"}
{"file":"txHandler.go","function":"github.com/algorand/go-algorand/data.(*solicitedAsyncTxHandler).loop","level":"info","line":541,"msg":"solicitedAsyncTxHandler was unable to relay transaction message : %!v(MISSING)","time":"2021-10-20T23:18:40.228828Z"}
{"file":"txHandler.go","function":"github.com/algorand/go-algorand/data.(*solicitedAsyncTxHandler).loop","level":"info","line":541,"msg":"solicitedAsyncTxHandler was unable to relay transaction message : %!v(MISSING)","time":"2021-10-20T23:18:40.228893Z"}
{"file":"txHandler.go","function":"github.com/algorand/go-algorand/data.(*solicitedAsyncTxHandler).loop","level":"info","line":541,"msg":"solicitedAsyncTxHandler was unable to relay transaction message : %!v(MISSING)","time":"2021-10-20T23:18:40.228946Z"}
{"file":"txHandler.go","function":"github.com/algorand/go-algorand/data.(*solicitedAsyncTxHandler).loop","level":"info","line":541,"msg":"solicitedAsyncTxHandler was unable to relay transaction message : %!v(MISSING)","time":"2021-10-20T23:18:40.229012Z"}
{"file":"txHandler.go","function":"github.com/algorand/go-algorand/data.(*solicitedAsyncTxHandler).loop","level":"info","line":541,"msg":"solicitedAsyncTxHandler was unable to relay transaction message : %!v(MISSING)","time":"2021-10-20T23:18:40.229080Z"}
```

## Test Plan

No test changes.

Author: cce

data/txHandler.go

@@ -538,7 +538,7 @@ func (handler *solicitedAsyncTxHandler) loop(ctx context.Context) {
 				// We reencode here instead of using rawmsg.Data to avoid broadcasting non-canonical encodings
 				err := handler.txHandler.net.Relay(ctx, protocol.TxnTag, reencode(txnGroup.Transactions), false, groups.networkPeer)
 				if err != nil {
-					logging.Base().Infof("solicitedAsyncTxHandler was unable to relay transaction message : %v")
+					logging.Base().Infof("solicitedAsyncTxHandler was unable to relay transaction message : %v", err)
 					break
 				}
 			}