releng-azure: Add ZFS support to Azure image buliding and uploading

Approved by: gjb (re), delphij (re)
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D41454

(cherry picked from commit 78f901dcbd84ccad3849a8029f2320cf97079856)
(cherry picked from commit 1e7218e33974089234841420bb69777a29a91c61)