UI Provision code to filter Amazon instance types

https://bugzilla.redhat.com/show_bug.cgi?id=1133780

The instance types are filtered based on the virtualization
type specified in the AMI. Each instance can support 1 or more
kind(s) of virtualization: hvm, paravirtual. Each AMI has a
virtualization type, so based on the selected AMI we can whittle
down the list of applicable instance types.
Instead of just checking the length, it would probably be a better test to verify you got the actual record you expected.  In the before, set it to an instance variable and then compare.  For the next test you can do the same thing, but use match_array instead of == because of the order independence.