Abuse sudo to ensure the lockfile is writable.
Abuse sudo to ensure the lockfile is writable.

Additionally, adjust the locking so anyone debugging issues can
tell exactly which point in the code it's hung waiting for access to.

Finally, the chroot name is incorporated into the lock to address the
scenario where people have multiple chroots in the same dir (haven't seen
it, but I'm removing all potentials here).

BUG=None
TEST=cd ${repo_root};touch .chroot_lock;sudo chown root .chroot_lock && cros_sdk

Change-Id: I0bdd97757040e0f1d35ba94f25319286988dda1f
Reviewed-on: https://gerrit.chromium.org/gerrit/15799
Reviewed-by: Ryan Cui <5ce1592d53754a87a44fc2eb7b63d5f77cf50fdb@chromium.org>
Commit-Ready: Brian Harring <fdc2d0a2e2340b623587cee5ea8dff425d1eb1f3@chromium.org>
Tested-by: Brian Harring <fdc2d0a2e2340b623587cee5ea8dff425d1eb1f3@chromium.org>

chadversary/chromiumos.chromite,coreos/chromite,coreos/chromite,bpsinc-native/src_third_party_chromite,coreos/chromite,zhang0137/chromite,bpsinc-native/src_third_party_chromite,zhang0137/chromite,bpsinc-native/src_third_party_chromite,zhang0137/chromite,chadversary/chromiumos.chromite