misc: Use job id and make short path for testdir

Nightlies run on teuthology currently use a testdir of
/home/ubuntu/cephtest, but this causes stale job errors occasionally
from the previous tests not getting properly cleaned up, which prevents
the nightlies from running successfully.

The misc.py get_testdir() function can specify a testdir that is
specific to the job, but previously the path was too long and would
cause separate job failures.

This patch does two things to resolve that.  First, it uses the job id
from the teuthology run if one exists.  This should be a relatively
short number that will identify the job run effectively.  Second,
if the job id isn't available, it creates a shortened form of the
job's name, for example the job name:

teuthology-2013-04-09_23:51:49-rgw-next-testing-basic

becomes:

te1304092351rntb

Signed-off-by: Sam Lang <sam.lang@inktank.com>
lock: Fix import cycle breakage

fa2049f caused an import cycle between lock.py and misc.py.  Move the
needed functions from lock.py to lockstatus.py so that we can avoid the
import cycle.

Signed-off-by: Sam Lang <sam.lang@inktank.com>

Conflicts:
	teuthology/lock.py
misc: Fix name parsing

Use last two digits of year.

Signed-off-by: Sam Lang <sam.lang@inktank.com>
misc: Use pythonic 'is not None' for jobid case

The conditional 'if global_jobid:' evaluates to true
in some cases even when global_jobid is None.

Signed-off-by: Sam Lang <sam.lang@inktank.com>
misc: Check for 'None' string from yaml

The description attribute from the machines yaml returned by the
locker might be the string 'None'.  Need to explicitly check for
that to avoid using a test dir of /tmp/cephtest/None.

Signed-off-by: Sam Lang <sam.lang@inktank.com>