Enable passing arbitrary ports to EC2 security group

Currently Beaker's EC2 provisioner creates a dynamic security group with port settings based on the role assigned in the SUT definition file.

However there is often a need for external access to ports not assigned to a static role. This patch allows an arbritrary number of additional ports to be added via an array, and maintains backward compatibility by setting the default value to an empty array.

Ideally the hardcoded ports should be pulled from this file, but this interim fix will broaden the supported functionality.