Fix SM paths in a generic way

Most of this change is a manual replace of paths such as "/opt/xensource/sm/foobar" with os.path.join(constants.SM_DEST,"foobar") and similar.

Moved the patches here rather than a seperate repo so we can bump our SM version more easily.
These patches (except xcp-sm-scsi-id-path.patch) will be proposed upstream once they are tested + shown to be stable here.