Fix gometalinter errors

Also disable test linters since we already run tests.

.gometalinter.json

@@ -18,8 +18,6 @@
     "megacheck",
     "safesql",
     "structcheck",
-    "test",
-    "testify",
     "unconvert",
     "unparam",
     "varcheck",

server/events/working_dir.go

@@ -154,7 +154,7 @@ func (w *FileWorkspace) forceClone(log *logging.SimpleLogger,
 	}
 
 	for _, args := range cmds {
-		cmd := exec.Command(args[0], args[1:]...)
+		cmd := exec.Command(args[0], args[1:]...) // nolint: gosec
 		cmd.Dir = cloneDir
 
 		cmdStr := w.cmdAsSanitizedStr(cmd, p.BaseRepo, headRepo)