Add logic to prevent large bandwidths from being used with ExpressRoutes

[jonstout]

After we do an initial fetch of the ExpressRoute's details check the bandwidth. If it's 10Gb reject and return an error to the user indicating lack of support; Request they modify their ExpressRoute to use a lower bandwidth.

https://github.com/GlobalNOC/OESS/blob/master/perl-lib/OESS/lib/OESS/Cloud.pm#L161-L170

Extra credit:
Instead of hard coding 10Gb as the rejection level, make it configurable.

[jonstout]

Part of the solution to this request should probably involve refactoring OESS::Entity->select_interface to return errors vs just logging them.

The bandwidth restriction could be setup in the Azure module on a per-interconnect basis?

[jonstout]

Azure 100Gb Interfaces should allow upto 10Gb connections
Azure 10Gb Interfaces should allow upto 5Gb connections