Adds get default share type function

This patch set adds the get default share type
function to client used by our tempest tests.

Also leverages this new function to get the default
share type, instead of using the get share types
command which was breaking in case the default
share type name was different than "default"

Closes-Bug: #1905796
Change-Id: If3508cd17a8640e88b21110d1d61dc424b94709e
2 files changed