Remove install_venv_common from openstack-common.conf

This is not actually used right now, so remove it.

Change-Id: I086bf4df2f0f4530725dcab5349ad20079f368ac
Import logging from oslo-incubator

The oslo-incubator repository of shared OpenStack code includes a
logging lib.  Import it and its depenencies.

For more information about oslo-incubator and using code from there,
see: https://wiki.openstack.org/wiki/Oslo#Incubation

This code was pulled from oslo-incubator at commit
cbfded9c0ddc80cf5422a0d65ffbd8e9a8714d45.

Part of blueprint logging

Change-Id: I2f6a2cf564903d1273105a4acedcc83e89cb207b