Use the encryption provider constants

... instead of the encryptor classes, whose direct usage has been
deprecated since Ocata.
See also Id221414d74af8413084c7935b762f93b7ce43c42 which applied
those changes to tempest.git.

Change-Id: I05b0200b80d8ae957caaa53d5006b050d2d49da6
1 file changed