Add Ruby 2.2.2 validation test for NArray gem

[kraushm]

Ruby 2.2.2 cannot be re-build on the Kesch nodes with the new OS and MCH is not yet able to move completely to Ruby 2.4, in particular with respect to the NArray gem. This ReFrame test is intended to validate the temporary work around, i. e. trying to use the current module of Ruby on the node with the upgraded OS.

This is the small test provided by MCH:

   #!/usr/bin/env ruby

   require "rubygems"
   require 'gsl'

   g1 = GSL::Vector.alloc(1,2,3,4)
   a1 = g1.to_na

   p a1

The result should look like this:

NArray.float(4):
 
[ 1.0, 2.0, 3.0, 4.0 ]