sergiusens lifecycle: query for multipass install on darwin (#2427)
Now that multipass is offered through a homebrew cask, it makes sense
to have a similar experience as offered on a snap enabled system.

LP: #1807737

Signed-off-by: Sergio Schvezov <sergio.schvezov@canonical.com>
Latest commit e9ae8d2 Dec 13, 2018