treewide: run gofmt -s and enable linter

Change-Id: I90b8ef48c955dccfddc5bbc0a57205b7da844b60
Reviewed-on: https://review.monogon.dev/c/monogon/+/3828
Tested-by: Jenkins CI
Reviewed-by: Leopold Schabel <leo@monogon.tech>
diff --git a/cloud/shepherd/manager/provider_test.go b/cloud/shepherd/manager/provider_test.go
index c88c996..3f6b139 100644
--- a/cloud/shepherd/manager/provider_test.go
+++ b/cloud/shepherd/manager/provider_test.go
@@ -96,8 +96,8 @@
 }
 
 type dummyProvider struct {
-	capacity int
-	machines map[shepherd.ProviderID]*dummyMachine
+	capacity   int
+	machines   map[shepherd.ProviderID]*dummyMachine
 	muMachines sync.RWMutex
 }