refactor: moved all fatal errors to logrus

This will allow us to test commands that would normally exit

client/connection.go

@@ -1,12 +1,15 @@
 package client
 
-import "github.com/docker/cli/cli/connhelper"
+import (
+	"github.com/docker/cli/cli/connhelper"
+	"github.com/sirupsen/logrus"
+)
 
 func newConnectionHelper(daemonURL string) *connhelper.ConnectionHelper {
 	helper, err := connhelper.GetConnectionHelper(daemonURL)
 
 	if err != nil {
-		panic(err)
+		logrus.Fatal(err)
 	}
 	return helper
 }