Updated service.py and its dependencies

This is to avoid service module dependency on importutils that are now
moved to oslo.utils.

The following changes are included:

 * neutron/openstack/common/eventlet_backdoor.py
  5d40e14 Remove code that moved to oslo.i18n
  90ae24b Remove redundant default=None for config options
  fcf517d Update oslo log messages with translation domains

 * neutron/openstack/common/loopingcall.py
  5d40e14 Remove code that moved to oslo.i18n
  e377393 Changes calcuation of variable delay
  ab5d5f1 Use timestamp in loopingcall
  bc48099 Log the function name of looping call
  fb4e863 Remove deprecated LoopingCall
  fcf517d Update oslo log messages with translation domains

 * neutron/openstack/common/service.py
  5d40e14 Remove code that moved to oslo.i18n
  6ede600 rpc, notifier: remove deprecated modules

 * neutron/openstack/common/systemd.py
  17c4e21 Fix docstring indentation in systemd

 * neutron/openstack/common/threadgroup.py
  5a1a016 Make stop_timers() method public
  fdc8883 Add graceful stop function to ThreadGroup.stop
  2d06d6c Simple typo correction
  4d18b57 threadgroup: use threading rather than greenthread

Change-Id: I4887545f861a93223e2c7cbcdd39efe991bff547
Updated cache module and its dependencies

This is to avoid cache module dependency on timeutils that are now moved
to oslo.utils.

The following changes are included:

 * neutron/openstack/common/cache/_backends/memory.py
  6ff6b4b Switch oslo-incubator to use oslo.utils and remove old modules
  2bedce3 Fix MemoryBackend not purging item from _keys_expired on delete

 * neutron/openstack/common/cache/backends.py
  39625e1 Set pbr 'warnerrors' option for doc build

 * neutron/openstack/common/cache/cache.py
  9c683be fix small typo

 * neutron/openstack/common/lockutils.py
  5d40e14 Remove code that moved to oslo.i18n
  7209975 Always log the releasing, even under failure
  bbb266c Clarify logging in lockutils
  942e1aa Use file locks by default again
  ac995be Fix E126 pep8 errors
  15b8352 Remove oslo.log from lockutils

Change-Id: I02cb4b2bc4b7bcba948e67cffdb8bd0219c89a29
Merge "Updated service.py and its dependencies"
Merge "Updated cache module and its dependencies"