Remove "Resize Instance" link from instances.

Apparently it is unsupported by the back-end systems but Havana has no
simple option to disable it via policies.  The link can be disabled
with a policy in Icehouse so this is just a temporary workaround.

Partial-rally-bug: DE571
Not-in-upstream: true
Merge branch 'bug/DE571' of github.com:ameoba/horizon into bug/DE571