Remove use of UniquePtr from keystore

Remove UniquePtr from keystore in favour of std::unique_ptr

(cherry picked from commit ccfff10f66d568b91ed155a798c5eaac2551f160)

Test: m
Merged-In: I8e02adab4326028e26dbf59ac836679abe2a40de
Change-Id: I8e02adab4326028e26dbf59ac836679abe2a40de
6 files changed