Add a bind mount of /dev to the chroot.
Add a bind mount of /dev to the chroot.

This is useful for various JTAG and fastboot based flashing of
targets.  It is also useful in that we will now have access to
USB card readers and mass storage devices inside the chroot.

BUG=None
TEST=Enter and exit the chroot cleanly.

Review URL: http://codereview.chromium.org/1711016

BugRoger/scripts,gtank/scripts,trnubo/scripts,marineam/coreos-scripts,zhang0137/scripts,gtank/scripts,andrejro/coreos--scripts,marineam/coreos-scripts,bcwaldon/coreos-scripts,BugRoger/scripts,smilart/scripts,marineam/coreos-scripts,vmware/coreos-scripts,trnubo/scripts,sigma/coreos-scripts,bcwaldon/coreos-scripts,zhang0137/scripts,crawford/scripts,mjg59/scripts,mischief/scripts,crawford/scripts,mischief/scripts,trnubo/scripts,andrejro/coreos--scripts,fivethreeo/scripts,glevand/coreos--scripts,bcwaldon/coreos-scripts,coreos/scripts,crawford/scripts,nicescale/scripts,endocode/scripts,vmware/coreos-scripts,fivethreeo/scripts,vmware/coreos-scripts,sigma/coreos-scripts,nicescale/scripts,glevand/coreos--scripts,fivethreeo/scripts,smilart/scripts,mjg59/scripts,mischief/scripts,coreos/scripts,andrejro/coreos--scripts,smilart/scripts,endocode/scripts,BugRoger/scripts,sigma/coreos-scripts,gtank/scripts,mjg59/scripts,nicescale/scripts,zhang0137/scripts,endocode/scripts