chg: [performance] fix for events with large numbers of attributes and multiple tags from the same taxonomy

- the taxonomy conflict checks were causing multiple issues:

- non taxonomy tags were counted as a taxonomy with namespace ''
- once we identified a tag pair that could cause a conflict (same taxonomy) we loaded the taxonomy into redis
  - however, in order to see if we already have the taxonomy loaded, we went to redis to do a GET
  - In the case of 1 million attributes with at least 1 tag pair, at the minimum this means 1 million GETs on reddit with an event

- Resolution
  - remove the checks for non taxonomy tags
  - store the identified taxonomies temporarily on the model itself in memory
    - only go to redis when the model doesn't have the taxonomy cached in memory
    - still using the old approach when dealing with multiple small events

- thanks to @github-germ for flagging the issue

app/Model/Taxonomy.php

@@ -33,6 +33,8 @@ class Taxonomy extends AppModel
         )
     );
 
+    private $__taxonomyConflicts = [];
+
     public function update()
     {
         $existing = $this->find('all', array(
@@ -593,7 +595,6 @@ class Taxonomy extends AppModel
         if ($splits === null) {
             return false; // not a taxonomy tag
         }
-
         $key = "misp:taxonomies_cache:tagName=$tagName&fullTaxonomy=$fullTaxonomy";
 
         try {
@@ -729,13 +730,19 @@ class Taxonomy extends AppModel
         $conflictingTaxonomy = array();
         foreach ($tagNameList as $tagName) {
             $tagShortened = $this->stripLastTagComponent($tagName);
+            // No exclusivity in non taxonomy tags.
+            if ($tagShortened === '') {
+                continue;
+            }
             if (isset($potentiallyConflictingTaxonomy[$tagShortened])) {
-                $potentiallyConflictingTaxonomy[$tagShortened]['taxonomy'] = $this->getTaxonomyForTag($tagName);
+                if (!isset($this->__taxonomyConflicts[$tagShortened])) {
+                    $this->__taxonomyConflicts[$tagShortened] = $this->getTaxonomyForTag($tagName);
+                }
                 $potentiallyConflictingTaxonomy[$tagShortened]['count']++;
             } else {
-                $potentiallyConflictingTaxonomy[$tagShortened] = array(
+                $potentiallyConflictingTaxonomy[$tagShortened] = [
                     'count' => 1
-                );
+                ];
             }
             $potentiallyConflictingTaxonomy[$tagShortened]['tagNames'][] = $tagName;
         }
@@ -747,9 +754,9 @@ class Taxonomy extends AppModel
         ) {
             unset($potentiallyConflictingTaxonomy['tlp']);
         }
-        foreach ($potentiallyConflictingTaxonomy as $potTaxonomy) {
+        foreach ($potentiallyConflictingTaxonomy as $taxonomyName => $potTaxonomy) {
             if ($potTaxonomy['count'] > 1) {
-                $taxonomy = $potTaxonomy['taxonomy'];
+                $taxonomy = $this->__taxonomyConflicts[$taxonomyName];
                 if (isset($taxonomy['Taxonomy']['exclusive']) && $taxonomy['Taxonomy']['exclusive']) {
                     $conflictingTaxonomy[] = array(
                         'tags' => $potTaxonomy['tagNames'],