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During BMC FW update, preserve the following directories:
  /var/cache/obmc/ - Holds the inventory data
  /var/lib/obmc/ - Holds the settings properties
The whiltelist is recursive, specifying /var/lib/obmc/
will still preserve the event log directory
/var/lib/obmc/events/, so it can be removed.

Change-Id: I1e1adb1b39a499a6c50e34171a964ee8c884f6c9
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>