add strip_cert_header() to tasks.py

https://pagure.io/freeipa/issue/7687

Reviewed-By: Rob Crittenden <rcritten@redhat.com>
Reviewed-By: Tibor Dudlak <tdudlak@redhat.com>

ipatests/pytest_ipa/integration/tasks.py

@@ -1531,3 +1531,16 @@ def generate_ssh_keypair():
 
     return (private_key_str, public_key_str)
 
+
+def strip_cert_header(pem):
+    """
+    Remove the header and footer from a certificate.
+    """
+    regexp = (
+        r"^-----BEGIN CERTIFICATE-----(.*?)-----END CERTIFICATE-----"
+    )
+    s = re.search(regexp, pem, re.MULTILINE | re.DOTALL)
+    if s is not None:
+        return s.group(1)
+    else:
+        return pem