[PR #6294/cb3ca05b backport][stable-6] one_vm: fix syntax error when creating VMs with a more complex template (#6342)

one_vm: fix syntax error when creating VMs with a more complex template (#6294)

* one_vm: fix syntax error when creating VMs with a more complex template

with more complex templates that make use of quoted strings the new
"render" method fails to produce a template that is accepted by
OpenNebula.  ==> escape double quotes in strings to make OpenNebula
happy again.

I also tested whether newlines need to be escaped, looks like they are
fine as they are.

Fixes #6225

* module_utils/opennebula: skip empty values in render

(cherry picked from commit cb3ca05bd1)

Co-authored-by: Georg Gadinger <nilsding@nilsding.org>

tests/unit/plugins/module_utils/test_opennebula.py

@@ -75,6 +75,18 @@ RENDER_VALID = [
             NIC=[NAME="NIC1",NETWORK_ID="1"]
         ''').strip()
     ),
+    (
+        {
+            'EMPTY_VALUE': None,
+            'SCHED_REQUIREMENTS': 'CLUSTER_ID="100"',
+            'BACKSLASH_ESCAPED': "this is escaped: \\n; this isn't: \"\nend",
+        },
+        textwrap.dedent('''
+            BACKSLASH_ESCAPED="this is escaped: \\\\n; this isn't: \\"
+            end"
+            SCHED_REQUIREMENTS="CLUSTER_ID=\\"100\\""
+        ''').strip()
+    ),
 ]