map bool -> map struct{} (#2386)

This clear out the remaining map[x]bool usage and moves the bool to an
empty struct.

Two note worthy other changes:

* EnableChaos in the server is now also exported to make it show up in
  the documentation.
* The auto plugin is left as is, because there the boolean is
  explicitaly set to false to signal 'to-be-deleted' and the key is left
  as-is.

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/log/log_test.go

@@ -21,7 +21,7 @@ func TestLoggedStatus(t *testing.T) {
 	rule := Rule{
 		NameScope: ".",
 		Format:    DefaultLogFormat,
-		Class:     map[response.Class]bool{response.All: true},
+		Class:     map[response.Class]struct{}{response.All: struct{}{}},
 	}
 
 	var f bytes.Buffer
@@ -53,7 +53,7 @@ func TestLoggedClassDenial(t *testing.T) {
 	rule := Rule{
 		NameScope: ".",
 		Format:    DefaultLogFormat,
-		Class:     map[response.Class]bool{response.Denial: true},
+		Class:     map[response.Class]struct{}{response.Denial: struct{}{}},
 	}
 
 	var f bytes.Buffer
@@ -82,7 +82,7 @@ func TestLoggedClassError(t *testing.T) {
 	rule := Rule{
 		NameScope: ".",
 		Format:    DefaultLogFormat,
-		Class:     map[response.Class]bool{response.Error: true},
+		Class:     map[response.Class]struct{}{response.Error: struct{}{}},
 	}
 
 	var f bytes.Buffer