Storage Chassis support

Closes-Bug: #1385504
Issue: Duplicate crush ids were found when applying the modified
    crushmap. Issue was found during the Ganges provisioning.
Fix: The current ID find login in the crush map modification code
    is wrong. The current logic just greps for the number of ids
    in the crushmap and starts using the next id. But this doesnt
    work for the chassis code as the existing ids cannot be reused.
    Fix is made by finding the max id in the list using a numeric
    sort, instead of just finding the number of entries. Based on
    the value, the new id is created and used in the crushmap.
Test: Verified with the Ganges provisioning.

Change-Id: Ibfe6e07b0bfe1237a14dfd812d3458ae7702fd30