Plumb more of the error reporting through.

This doesn't fix the bug, but it does flatten the bug to the well-known
and long-standing "adb shell" doesn't return exit statuses, so when we
fix that, this one will fix itself.

Bug: http://b/20423886
Change-Id: I48351e46f05dd3f2f6e57f0df1d851333458d0ef