Set ClipData with attachments URIs on bugreport notification.

The ACTION_SEND_MULTIPLE contract expects the EXTRA_TEXT to be an
ArrayList<String>, but it's currently set as String, which causes an
exception when exporting the EXTRA_STREAM as ClipData.

The right approach would be changing the EXTRA_TEXT content, but that
would break some clients like GMail, so a safer fix is to explicitly
set the ClipData.

Also removed unused variables and imports.

BUG: 21735884
BUG: 21729227

 Changes to be committed:
	modified:   src/com/android/shell/BugreportReceiver.java

Change-Id: If9954e8cae4af7b74f077a32806f25eb7d55dffb