Fix scenario tests when default-subnetpools extension is absent

On some networking backends like Tungsten Fabric subnetpools
extensions are not supported, so usage of related arguments
when creating subnet should be avoided.

Related-Prod: https://mirantis.jira.com/browse/PRODX-49702
Change-Id: Ia76085810c34c1a0af064e137440b02d3edc9abe
(cherry picked from commit 51e6474676ade84b91b68117d1e004f91cf57b07)
diff --git a/manila_tempest_tests/tests/scenario/manager_share.py b/manila_tempest_tests/tests/scenario/manager_share.py
index 6d6efc0..94a8c91 100644
--- a/manila_tempest_tests/tests/scenario/manager_share.py
+++ b/manila_tempest_tests/tests/scenario/manager_share.py
@@ -17,6 +17,7 @@
 from urllib.request import urlopen
 
 from oslo_log import log
+from tempest.common import utils as common_utils
 from tempest.common import waiters
 from tempest import config
 from tempest.lib.common.utils import data_utils
@@ -114,10 +115,17 @@
         self.network = self.create_network(namestart="manila-share")
         # When not using a "storage network" to connect shares to VMs,
         # we need the subnet to match the IP version we're testing
-        subnet_ip_params = {} if self.storage_network else {
-            'ip_version': self.ip_version,
-            'use_default_subnetpool': self.ipv6_enabled
-        }
+        subnet_ip_params = {}
+        if not self.storage_network:
+            subnet_ip_params = {
+                'ip_version': self.ip_version,
+            }
+            if common_utils.is_extension_enabled(
+                "default-subnetpools",
+                "network"
+            ):
+                subnet_ip_params["use_default_subnetpool"] = self.ipv6_enabled
+
         self.subnet = self.create_subnet(
             network=self.network,
             namestart="manila-share-sub",