Call ISecretKeeper.deleteAll() from deleteSecrets()

deleteSecrets() is called from rebootRecoveryWithCommand () before the
--wipe_data command is passed to recovery and the device is
force-rebooted.

Calling ISecretkeeper.deleteAll() destroys all secrets managed by
secretkeeper, thus ensuring that they are unrecoverable even if the full
data wipe in recovery is interrupted or skipped.

Bug: 324321147
Test: Manual - System -> Reset options -> Erase all data.
Test: Hold VolDown key to interrupt reboot and stop at bootloader
screen.
Test: fastboot oem bcd wipe command && fastboot oem bcd wipe recovery
Test: fastboot reboot
Test: Device reboots into recovery and prompts to factory reset:
Test: 'Cannot load Android system. Your data may be corrupt. ...'

Change-Id: I4c1c6615c0877d447d06ae45dd8ff86f7f14685a