multi: fix linter issues

This commit fixes outstanding linter issues, that we're not found by
running `make lint` locally. The linter issues were found by running
`docker run -v $(pwd):/build loop-tools golangci-lint run --whole-files`

I added the `revive` to the excludes as it would be to much of a
refactor and IMO seems unneccesary. E.g.
`interface.go:222:6: exported: type name will be used as
loop.LoopInTerms by other packages, and that stutters; consider
 calling this InTerms (revive)`. I think `loop.LoopInTerms` is fine.

executor.go

@@ -38,7 +38,7 @@ type executorConfig struct {
 
 // executor is responsible for executing swaps.
 //
-// TODO(roasbeef): rename to SubSwapper
+// TODO(roasbeef): rename to SubSwapper.
 type executor struct {
 	wg            sync.WaitGroup
 	newSwaps      chan genericSwap
@@ -134,9 +134,9 @@ func (s *executor) run(mainCtx context.Context,
 
 	swapDoneChan := make(chan int)
 	nextSwapID := 0
+
 	for {
 		select {
-
 		case newSwap := <-s.newSwaps:
 			queue := queue.NewConcurrentQueue(10)
 			queue.Start()