Settings: Fix to display Paired Devices when Settings App is killed

Whenever Settings process is killed, the mCachedDevices list
containing the bonded devices is erased. After it starts, UI doesn't
show any paired devices as the list is empty. This fix adds the
paired devices back to the mCachedDevices after Settings process
starts.

CRs-Fixed: 816355
Change-Id: I5caebe8d0fd3f5767dd5afca2dfc0d4c1811c176