make announcement search consistent with discussions

test plan:
 - have a multi-word title in an announcement
   (e.g. "Announcement 1")
 - have another announcement that shares one word
   but not the entire phrase
   (e.g. "Announcement 2")
 - on the announcements page, search for the entire phrase.
   only the announcement matching the entire phrase should
   result ("Announcement 1" should not match "Announcement 2").

fixes CNVS-28657

Change-Id: If8962b396394ebaf38596bd4164c67576680f32f
Reviewed-on: https://gerrit.instructure.com/77832
Tested-by: Jenkins
Reviewed-by: Joel Hough <joel@instructure.com>
QA-Review: Deepeeca Soundarrajan <dsoundarrajan@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>

Author: jstanley0

app/coffeescripts/views/announcements/IndexView.coffee

@@ -183,10 +183,8 @@ define [
       onlyGraded: -> @get 'assignment_id'
       onlyUnread: -> (@get('read_state') is 'unread') or @get('unread_count')
       searchTerm: (term) ->
-        words = term.match(/\w+/ig)
-        pattern = "(#{_.uniq(words).join('|')})"
-        regexp = new RegExp(pattern, "igm")
-
+        return unless term
+        regexp = new RegExp(term, "ig")
         @get('author')?.display_name?.match(regexp) ||
           @get('title').match(regexp) ||
           @summary().match(regexp)

spec/selenium/announcements/announcements_teacher_spec.rb

@@ -59,6 +59,11 @@
         refresh_and_filter(:string, 'jake', user_name)
       end
 
+      it "should search an entire phrase" do
+        replace_content(f('#searchTerm'), 'new 001')
+        expect(ff('.discussionTopicIndexList .discussion-topic').count).to eq 1
+      end
+
       it "should return multiple items in the search", priority: "1", test_id: 220362 do
         new_title = 'updated'
         what_to_create.first.update_attributes(:title => "#{new_title} first")