storaged: call getNamesForUids to get uid names

Calls getNamesForUids when one of the two conditions are true.
1. entries for new uids are reported from io stats
2. previous getNamesForUids failed

Bug: 62805090
Merged-In: I120b81e1857b2aa0a90d0fb85c8d749e985df78e
Change-Id: I120b81e1857b2aa0a90d0fb85c8d749e985df78e