Fix StorageManagerTest#testCallback

Added per-user id volume check instead of assuming "0"

Test: atest --user-type secondary_user StorageManagerTest
Bug: 191697126
Change-Id: I122650374c55d3833720fc992be01dba37b3a486
(cherry picked from commit b0545d30745c35f8d5a58d55c9bb35d356bcdd17)