Secure root password on restore from backup after root-enable

On the restore of an instance that has root enabled on it, we need
to ensure that we are correctly securing the root password so that
the password is not empty.

Fixes bug: 1211557

Change-Id: I6386b9e0573a39a6667504666556b918927abf76
Merge "Secure root password on restore from backup after root-enable"