scripts: bind ~/.ssh over the chroot's ~/.ssh.
scripts: bind ~/.ssh over the chroot's ~/.ssh.

This also mounts the path to our ssh-agent socket (usually in /tmp) inside the
chroot so we can use our external agent.

TEST=None

BUG=None

Change-Id: I543e8b2527be9958c1158234f39ecc34fc9dd0df
Signed-Off-By: Elly Jones <ellyjones@chromium.org>
Signed-Off-By: sosa <sosa@chromium.org>

Review URL: http://codereview.chromium.org/3277006

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