FIX: Stop infinite lookup-urls issue for video/audio on page (#9096)

Meta report: https://meta.discourse.org/t/excessive-requests-to-uploads-lookup-urls-leading-to-429-response/143119

* The data-orig-src attribute was not being removed from cooked
video and audio so the composer was infinitely trying to get the
URLs for them, which would never resolve to anything
* Also the code that retrieved the short URL was unscoped, and was
getting everything on the page. if running from the composer we
now scope to the preview window
* Also fixed a minor issue where the element href for the video
and audio tags was not being set when the short URL was found

test/javascripts/lib/upload-short-url-test.js.es6

@@ -23,6 +23,11 @@ QUnit.module("lib:pretty-text/upload-short-url", {
         short_url: "upload://b.jpeg",
         url: "/uploads/default/original/3X/c/b/2.jpeg",
         short_path: "/uploads/short-url/b.jpeg"
+      },
+      {
+        short_url: "upload://z.jpeg",
+        url: "/uploads/default/original/3X/c/b/9.jpeg",
+        short_path: "/uploads/short-url/z.jpeg"
       }
     ];
 
@@ -53,7 +58,8 @@ QUnit.module("lib:pretty-text/upload-short-url", {
 
     fixture().html(
       imageSrcs.map(src => `<img data-orig-src="${src.url}">`).join("") +
-        attachmentSrcs.map(src => `<a data-orig-href="${src.url}">`).join("")
+        attachmentSrcs.map(src => `<a data-orig-href="${src.url}">`).join("") +
+        `<div class="scoped-area"><img data-orig-src="${imageSrcs[2].url}"></div>`
     );
   },
 
@@ -105,3 +111,23 @@ QUnit.test("resolveAllShortUrls", async assert => {
     short_path: "/uploads/short-url/e.mp3"
   });
 });
+
+QUnit.test("resolveAllShortUrls - scoped", async assert => {
+  let lookup;
+  await resolveAllShortUrls(ajax, ".scoped-area");
+
+  lookup = lookupCachedUploadUrl("upload://z.jpeg");
+
+  assert.deepEqual(lookup, {
+    url: "/uploads/default/original/3X/c/b/9.jpeg",
+    short_path: "/uploads/short-url/z.jpeg"
+  });
+
+  // do this because the pretender caches ALL the urls, not
+  // just the ones being looked up (like the normal behaviour)
+  resetCache();
+  await resolveAllShortUrls(ajax, ".scoped-area");
+
+  lookup = lookupCachedUploadUrl("upload://a.jpeg");
+  assert.deepEqual(lookup, {});
+});