MFA: Support multiple digest algos at a time

Summary: Marged in kolab_2fa changes from https://git.kolab.org/rRPKa2119c58f6d24533f11064127f356c546d66ef26

Test Plan: ./phpunit

Reviewers: #hkccp_developers, mollekopf

Reviewed By: #hkccp_developers, mollekopf

Subscribers: #hkccp_developers

Differential Revision: https://git.kolab.org/D4932