serialize: Add version purpose

Add store/restore of the version purpose. Only need to store it if the
activation was successful, since those are the only versions that are
restored after BMC reboot.

Tested: Verified a code update with an image of purpose System got its
        value restored instead of being set to BMC by default.

Change-Id: I6414e9f3b992a8c29046b4d3a3d581c20a166cee
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
5 files changed