[Extensions] Update more test extensions to manifest v2

Update chrome/test/data/extensions/permissions_increase/* to
manifest v2. This required changing background_page to
background.

Bug: 816679
Change-Id: I99afd26749acf1c7d8bf9b737200370de5324ba5
Reviewed-on: https://chromium-review.googlesource.com/946549Reviewed-by: Istiaque Ahmed <lazyboy@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540704}

chrome/test/data/extensions/permissions_increase/v1/manifest.json

 {
   "version": "1",
+  "manifest_version": 2,
   "name": "Permission Test",
-  "background_page": "background.html",
+  "background": { "page": "background.html" },
   "update_url": "http://localhost/autoupdate/updates.xml"
 }

chrome/test/data/extensions/permissions_increase/v2/manifest.json

 {
   "version": "2",
+  "manifest_version": 2,
   "name": "Permission Test",
-  "background_page": "background.html",
+  "background": { "page": "background.html" },
   "update_url": "http://localhost/autoupdate/updates.xml",
   "permissions": [
     "tabs"

chrome/test/data/extensions/permissions_increase/v3/manifest.json

 {
   "version": "3",
+  "manifest_version": 2,
   "name": "Permission Test",
-  "background_page": "background.html",
+  "background": { "page": "background.html" },
   "update_url": "http://localhost/autoupdate/updates.xml",
   "permissions": [
     "tabs", "management"