Add additional shortcutExists check to prevent same app from being auto added.

Since we made the change to treat all auto added workspace items as promise
icons, the initial shortcutExists check breaks since its comparing the promise
intent to the actual app intent. This additional shortcutExists check can
compare the proper intents.

Bug: 143803446
Change-Id: Ifa27b15205d6e17f83a4437ac175d51815688c84