SCTX-1585: Handle hosts having different lists of features

During an upgrade, the older hosts will not indicate whether or not they
support newer features. If a host doesn't support a feature, always
treat as restricted on that host for the purposes of working out the
pool restrictions.

Signed-off-by: John Else <john.else@citrix.com>
SCTX-1585: Get additional features from the master

Use the master's license_params as the "definitive" list of features,
rather than just picking a host at random.

Signed-off-by: John Else <john.else@citrix.com>
Merge pull request #1566 from johnelse/sctx-1585-pr-1675

SCTX-1585: master defines pool features; handle hosts with varied feature-sets