Add recursive getter functions

When transforming a NodeConf struct to a NodeInfo (get the NodeInfo from
the Nodconf) nested structures were seperately handled. This means there
were seperate handles for e.g *Netdevs and *IpmiConfig. The new getter
traverses through the datastucture and sets the right value for an Entry
struct, but calls itself again if a Pointer is detected.

This adds the posiblity to add new nested structures to NodeConf and
NodeInfo without the need of seperate handling them in the transformer
functions.

Signed-off-by: Christian Goll <cgoll@suse.de>

internal/pkg/node/transformer_test.go

@@ -299,13 +299,14 @@ ipmi: {}
 			t.Errorf("Got wrong yml, wanted:\n'%s'\nGot:\n'%s'", wanted, string(ymlByte))
 		}
 		delete(test_node4.Tags, "foo")
+		nodeConf = NewConf()
 		nodeConf.GetFrom(test_node4)
 		nodeConf.Flatten()
 		ymlByte, _ = yaml.Marshal(nodeConf)
 		wanted = `{}
 `
 		if string(ymlByte) != wanted {
-			t.Errorf("Couldn't remove tag'%s'", string(ymlByte))
+			t.Errorf("Couldn't remove tag, wanted:\n%s\nGot:\n%s", wanted, string(ymlByte))
 		}
 
 	})