test(inspec): display proper diff when `_mapdata` mismatch

The use of `eq` instead of `include` premits to have a nice diff after
the `expected/got` oneliners.

test/integration/default/controls/_mapdata_spec.rb

 
   describe file('/tmp/salt_mapdata_dump.yaml') do
     it { should exist }
-    its('content') { should include mapdata_dump }
+    its('content') { should eq mapdata_dump }
   end
 end