No need to remove profile encryption key on boot

PROFILE_KEY_NAME_ENCRYPT is a temporary encryption key used during
profile challenge unification to encrypt the profile password. It's
deleted right after the unification process so there is no need to
keep trying deleting it during each boot. Also add a log when profile
decryption key is removed.

Both of these changes are speculative fixes for a reported issue
where profile unification is broken midway.

Bug: 143946738
Test: builds
Change-Id: I382010150ddbab49c8c9971a1d0a97dff5c86271