Create a new module for lxc code.

Create a new python module for lxc code.  Move lxc.py and related code into that
module. Script-style functionality in site_utils/lxc.py and lxc_cleanup.py was
left as-is.

BUG=chromium:720219
TEST=sudo python site_utils/lxc_functional_test.py -v
     2017-06-15 15:29:52,700 All tests passed.
TEST=Install autotest-server code onto moblab, run a test.
     Test runs successfully.

Change-Id: I7b8400db64594f4d1268a62838ac379e713738c1
Reviewed-on: https://chromium-review.googlesource.com/538127
Commit-Ready: Ben Kwa <kenobi@chromium.org>
Tested-by: Ben Kwa <kenobi@chromium.org>
Reviewed-by: Ben Kwa <kenobi@chromium.org>
diff --git a/server/autoserv b/server/autoserv
index bdc47a9..0a7f520 100755
--- a/server/autoserv
+++ b/server/autoserv
@@ -53,7 +53,7 @@
 from autotest_lib.site_utils import job_directories
 from autotest_lib.site_utils import job_overhead
 from autotest_lib.site_utils import lxc
-from autotest_lib.site_utils import lxc_utils
+from autotest_lib.site_utils.lxc import utils as lxc_utils
 from autotest_lib.client.common_lib import pidfile, logging_manager