2f55dc28c5 [1] suggests that the underscore naming convention might be somewhat entrenched ("the container's hostname must start with `test_` to allow DHCP server in Moblab to set a correct lease time")

Need to modify /etc/dhcp/dhcpd-moblab.conf for this.

1: https://chromium.googlesource.com/chromiumos/third_party/autotest/+/2f55dc28c5

As discussed earlier, renaming should be fine. sponge doesn't use it, moblab will take care of the change and I hope Jason's dashboard can handle it as well (but need to confirm).

Internal dashboard should be ok as we are currently only recording it. It's used in the sponge link to get the invocation:
(e.g. https://sponge.corp.google.com/invocations?quickSearch=chromeos2-row7-rack10-host15+label%3Aboard%3Aelm+label%3Abuild%3Aelm-release%2FR60-9583.0.0+user%3Achromeos-test+label%3Asuite%3Aarc-cts+CtsCompilationTestCases)
As long as what's exported to sponge is consistent I think renaming should be fine.

Re #4

The sponge record is generated after the test is finished. So it doesn't happen inside the container. That's why the "Hostname" property in sponge record is the actual drone's FQDN.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/third_party/autotest/+/1eba6d21cac341717b678d8e475402bb2ebfde0a

commit 1eba6d21cac341717b678d8e475402bb2ebfde0a
Author: Ben Kwa <kenobi@google.com>
Date: Fri Jun 02 08:37:28 2017

Use hyphens in container hostnames.

Change from using underscores ('_') to hyphens ('-') in container
hostnames, as underscore is not actually a valid character in hostnames.

BUG= chromium:726131 
TEST=sudo python site_utils/lxc_functional_test.py -v
     2017-05-25 07:23:30,661 All tests passed.

Change-Id: I604da466ca9ea4ed9be0147ff11f46ac07f38dec
Reviewed-on: https://chromium-review.googlesource.com/515025
Commit-Ready: Ilja H. Friedel <ihf@chromium.org>
Tested-by: Ben Kwa <kenobi@chromium.org>
Reviewed-by: Ilja H. Friedel <ihf@chromium.org>
Reviewed-by: Jason Kusuma <jkusuma@chromium.org>
Reviewed-by: Dan Shi <dshi@google.com>

[modify] https://crrev.com/1eba6d21cac341717b678d8e475402bb2ebfde0a/site_utils/lxc_functional_test.py
[modify] https://crrev.com/1eba6d21cac341717b678d8e475402bb2ebfde0a/site_utils/lxc.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/board-overlays/+/e3bffef3fa3da4fee46729aaafbcbc075f4ae4da

commit e3bffef3fa3da4fee46729aaafbcbc075f4ae4da
Author: Keith Haddow <haddowk@chromium.org>
Date: Sat Jun 03 03:15:33 2017

[moblab] allow containers to have underscore or dash in the name.

TEST=None
BUG= chromium:726131 

Change-Id: I861a4ca9a8d7d08ec274b70b76e22d7f20a38a9b
Reviewed-on: https://chromium-review.googlesource.com/514330
Commit-Ready: Keith Haddow <haddowk@chromium.org>
Tested-by: Keith Haddow <haddowk@chromium.org>
Reviewed-by: Ilja H. Friedel <ihf@chromium.org>
Reviewed-by: Keith Haddow <haddowk@chromium.org>
Reviewed-by: Ben Kwa <kenobi@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
Reviewed-by: Dan Shi <dshi@google.com>

[modify] https://crrev.com/e3bffef3fa3da4fee46729aaafbcbc075f4ae4da/project-moblab/chromeos-base/chromeos-bsp-moblab/files/dhcpd-moblab.conf