When rendering the clone page, check user profile to decide default clone...

When rendering the clone page, check user profile to decide default clone protocol. If the user has uploaded SSH-keys, use SSH; otherwise, use http(s). Close #3504.

app/helpers/projects_helper.rb

@@ -175,11 +175,21 @@ module ProjectsHelper
   end
 
   def default_url_to_repo(project = @project)
-    current_user ? project.url_to_repo : project.http_url_to_repo
+    if default_clone_protocol == "ssh"
+      project.ssh_url_to_repo
+    else
+      project.http_url_to_repo
+    end
   end
 
   def default_clone_protocol
-    current_user ? "ssh" : "http"
+    if !current_user
+      "http"
+    elsif current_user.require_ssh_key?
+      "http"
+    else
+      "ssh"
+    end
   end
 
   def project_last_activity(project)