SI ext makes compute api calls. No unit tests.

scheduled images ext makes compute api calls instead of db for
operations on the system metadata. There are no unit tests for
the changes in this commit.

Change-Id: I72da0e9c32f7d5586754bfad56ecd19ed3200b08
Merge pull request #34 from rackspace-titan/extension-OS-SI-compute-api

Extension os si compute api