Cleanup bad JSON files

- Add missing commas
- Replace single quote with double quote
- events field contains a list of events (event-create-req.json)
- Remove empty files
- Adds a JSON validation test to the docs pipeline

Co-Authored-By: Nicolas Simonds <nic@metacloud.com>
Change-Id: I9a4a9b6b8e2da73b5f25145be3b2faa44ebdb340

doc/api_samples/os-floating-ip-dns/floating-ip-dns-create-or-update-entry-req.json

@@ -1,7 +1,6 @@
 {
-  'dns_entry' :
-    {
-      'ip': '192.168.53.11',
-      'dns_type': 'A'
-    }
+  "dns_entry": {
+    "ip": "192.168.53.11",
+    "dns_type": "A"
+  }
 }

doc/api_samples/os-floating-ip-dns/floating-ip-dns-create-or-update-req.json

@@ -1,8 +1,7 @@
 {
-  'domain_entry' :
-    {
-      'domain': 'domain1.example.org',
-      'scope': 'public',
-      'project': 'project1'
-   }
+  "domain_entry": {
+    "domain": "domain1.example.org",
+    "scope": "public",
+    "project": "project1"
+  }
 }