Avoid redundant unlock of newly created key

IVold.createUserKey unlocks the key that it creates, so the later call
to IVold.unlockUserKey is unnecessary and just triggers a warning:

    W vold    : Tried to unlock already-unlocked key for user 10

Avoid this by making the createUserKey and destroyUserKey methods of
StorageManagerService update the mLocalUnlockedUsers array, so that the
StorageManagerService state stays in sync with the vold state.

Test: pm create-user 10; am start-user 10; checked logcat
Bug: 232452368
Change-Id: I238b2b218582e2791b25998e8ebaa1004ca0466d