Disable CryptKeeper activity for secondary users

For secondary users, disable CryptKeeper activity in a broadcast receiver of
USER_INITIALIZE intent. This change has the following benefits for guest
user switching:
 - The code will be executed earlier in the user switching flow, when the
   screen is frozen by WindowManager.
 - Initialization of CryptKeeperActivity is skipped

Bug:18670536
Change-Id: I60300198b605c26ad15afe2c874d5f1be7da5087