fail with useful error on unmatched interface (bsc#990745)

If we fail to find an interface matching a pattern such as "+10g1"
for a given node, don't proceed blindly, but instead bail with a
helpful error message.

This helps more quickly identify incorrectly configured network.json
files, and was experienced in a scenario where the Crowbar nodes were a
mix of physical machines and VMs with slow virtio interfaces.

https://bugzilla.suse.com/show_bug.cgi?id=990745

chef/cookbooks/barclamp/libraries/barclamp_library.rb

@@ -165,7 +165,11 @@ def self.build_node_map(node)
           v.each do |mk, mv|
             if mk == "if_list"
               hash["if_list"] = v["if_list"].map do |if_ref|
-                map_if_ref(if_remap, if_ref)
+                r = map_if_ref(if_remap, if_ref)
+                if r.nil?
+                  raise "Unable to find interface for #{node.fqdn} matching #{if_ref} out of #{if_remap}"
+                end
+                r
               end
             else
               hash[mk] = mv