Add configuration option 'image_conversion_dir' for cinder.

Cinder configuration option 'image_conversion_dir' set path to directory
used for temporary storage during image conversion.

Change-Id: Icc01549730e6b9457a88cd933b877e9968384775
Related-Prod: PROD-29437 (PROD:29437)
(cherry picked from commit edaf7481d5616bd905911c502a070b6b45a69fa1)
5 files changed