properly count hosts based on job event task state

the intention of the host summary view is that each host belongs in at
most *one* state - determined by the state of the tasks that ran on it.
this change examines each host for a job and determines its state based
on whether tasks passed, resulted in changes, were skipped, failed,
etc...

see: #5407

awx/ui/tests/spec/job-results/job-results.service-test.js

@@ -0,0 +1,50 @@
+'use strict';
+
+describe('jobResultsService', () => {
+    let jobResultsService;
+
+    beforeEach(angular.mock.module('Tower'));
+
+    beforeEach(angular.mock.inject(( _jobResultsService_) => {
+        jobResultsService = _jobResultsService_;
+    }));
+
+    describe('getCountsFromStatsEvent()', () => {
+        it('properly counts hosts based on task state', () => {
+            let event_data = {
+                "skipped": {
+                    "skipped-host": 5  // this host skipped all 5 tasks
+                },
+                "ok": {
+                    "ok-host": 5,  // this host was ok on all 5 tasks
+                    "changed-host": 4  // this host had 4 ok tasks, had 1 changed task
+                },
+                "changed": {
+                    "changed-host": 1
+                },
+                "failures": {
+                    "failed-host": 1  // this host had a failed task
+                },
+                "dark": {
+                    "unreachable-host": 1  // this host was unreachable
+                },
+                "processed": {
+                    "ok-host": 1,
+                    "changed-host": 1,
+                    "skipped-host": 1,
+                    "failed-host": 1,
+                    "unreachable-host": 1
+                },
+                "playbook_uuid": "c23d8872-c92a-4e96-9f78-abe6fef38f33",
+                "playbook": "some_playbook.yml",
+            };
+            expect(jobResultsService.getCountsFromStatsEvent(event_data)).toEqual({
+                'ok': 1,
+                'skipped': 1,
+                'unreachable': 1,
+                'failures': 1,
+                'changed': 1
+            });
+        });
+    });
+});