EINTR from communication with subprocess in allmydata/util/iputil.py _query

[davidsarah]

Reported by 'sickness' on irc:

#   Run
#     test_loadable ...                                                      [OK]
#     test_reloadable ... Node._startService failed, aborting
# [Failure instance: Traceback: <type 'exceptions.OSError'>: [Errno 4] Interrupted system call
# /usr/lib/python2.6/threading.py:497:__bootstrap
# /usr/lib/python2.6/threading.py:525:__bootstrap_inner
# /usr/lib/python2.6/threading.py:477:run
# --- <exception caught here> ---
# /usr/lib/python2.6/vendor-packages/twisted/python/threadpool.py:210:_worker
# /usr/lib/python2.6/vendor-packages/twisted/python/context.py:59:callWithContext
# /usr/lib/python2.6/vendor-packages/twisted/python/context.py:37:callWithContext
# /home/righdieg/allmydata-tahoe-1.8.2/src/allmydata/util/iputil.py:222:_synchronously_find_addresses_via_config
# /home/righdieg/allmydata-tahoe-1.8.2/src/allmydata/util/iputil.py:237:_query
# /usr/lib/python2.6/subprocess.py:689:communicate
# /usr/lib/python2.6/subprocess.py:1233:_communicate
# /usr/lib/python2.6/subprocess.py:1157:wait
# ]
# calling os.abort()

Possibly related: ​http://bugs.python.org/issue1068268 . It may be that the patch for that bug wasn't complete enough. EINTR failures are usually not very reproducible, but the fix is just to repeat the query until it works (or fails with a different error).