Fix USB intent warning on deviceAttached()

Use sendBroadcastAsUser() in deviceAttached(), the same as
deviceDetached() does.

Attached generates log entry like this:
"Calling a method in the system process without a
 qualified user"
Example log: http://pastebin.com/UBWJR4KU (see line 30)

Change-Id: I2384a3cb2fd336adeb0077c5729ee3aa66c696ca