Set workspace into a transition prepare state before animating into all apps

Fix for:
https://jira.cyanogenmod.org/browse/BACON-594

Change-Id: I54c168174ebb9a2dd3147f4696caadec817eac4f
Revert "Fix AppInfo drop target bug"

This reverts commit 498c660baad57f84f2979d0e3e1ebcf45a23f05c.
The commit causes breaks adding widget shortcuts to the Workspace.
Ex: Floating calculator, contacts, etc.

Change-Id: I681669e6b26ddf3ae2dede0eb05532d6779b9aa2
Fixes bug with extra empty screen staying on Workspace when a
shortcut is dragged to the AppInfo target.

Change-Id: Ie223beed5226c75d287a5a8b7983578a01bc8391