Merge "Don't use default=None for config options"

diff --cc cinder/common/config.py
Simple merge

diff --cc cinder/volume/driver.py
Simple merge

diff --cc cinder/volume/drivers/cloudbyte/options.py
Simple merge

diff --cc cinder/volume/drivers/ibm/gpfs.py
Simple merge

diff --cc cinder/volume/drivers/ibm/storwize_svc/__init__.py
Simple merge

diff --cc cinder/volume/drivers/nfs.py
Simple merge

diff --cc cinder/volume/drivers/rbd.py
Simple merge

diff --cc cinder/volume/drivers/tintri.py
Simple merge

diff --cc cinder/volume/drivers/vmware/vmdk.py
Simple merge