Merge "fastboot: gracefully handle failure to open a USB device on OS X." am: 11be3e54bd am: 9a1e060dc6 am: 4a84cce540 am: 3cf521b16e
am: 53ef6c213e

Change-Id: I9eb9038f9cb6f6a15ae2d74dd615d964fc7f0041