Hide mr close button for comment form if merge request was closed or inline comment

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Conflicts:
	app/views/projects/merge_requests/_show.html.haml

app/assets/stylesheets/sections/merge_requests.scss

@@ -89,3 +89,8 @@
 .merge-request-form-info {
   padding-top: 15px;
 }
+
+// hide mr close link for inline diff comment form
+.diff-file .close-mr-link {
+ display: none;
+}

app/views/projects/merge_requests/_show.html.haml

@@ -24,8 +24,8 @@
   - content_for :note_actions do
     - if can?(current_user, :modify_merge_request, @merge_request)
-      - unless @merge_request.closed?
-        = link_to 'Close', project_merge_request_path(@project, @merge_request, merge_request: {state_event: :close }), method: :put, class: "btn grouped btn-close", title: "Close merge request"
+      - unless @merge_request.closed? || @merge_request.merged?
+        = link_to 'Close', project_merge_request_path(@project, @merge_request, merge_request: {state_event: :close }), method: :put, class: "btn grouped btn-close close-mr-link", title: "Close merge request"
   .notes.tab-content.voting_notes#notes{ class: (controller.action_name == 'show') ? "" : "hide" }