ASGARD-1177 - Instance types missing price info should be at bottom of instance drop-down, not top

Sometimes we display instance types in a drop-down without prices. Any time that happens, make sure the types that are missing price labels are at the bottom, not the top.
Update related unit tests
Merge pull request #390 from joesondow/ASGARD-1177-Instance-types-missing-price-belong-at-bottom

ASGARD-1177 - Instance types missing price info should be at bottom of instance drop-down, not top