openssl_certificate: Handle dump() in check_mode (#38386)

Currently, when ones run the module in check_mode it tries to retrieve
values from the actual certificate generated in the generate() function.

Since in check_mode we call dump() without calling generate(), self.cert
is None, leading to self.cert.get_notBefore(), self.cert.get_notAfter()
and self.cert.get_serial_number() raising an error.

>  NoneType' object has no attribute 'get_notBefore'

The solution is to have two way to handle dump() method, whether its run
in check_mode=True or check_mode=False leading to different way the
information is retrieved.

test/integration/targets/openssl_certificate/tasks/main.yml

@@ -28,6 +28,15 @@
         selfsigned_digest: sha256
       register: selfsigned_certificate_idempotence
 
+    - name: Generate selfsigned certificate (check mode)
+      openssl_certificate:
+        path: '{{ output_dir }}/cert.pem'
+        csr_path: '{{ output_dir }}/csr.csr'
+        privatekey_path: '{{ output_dir }}/privatekey.pem'
+        provider: selfsigned
+        selfsigned_digest: sha256
+      check_mode: yes
+
     - name: Check selfsigned certificate
       openssl_certificate:
         path: '{{ output_dir }}/cert.pem'