Remove experimental flag from share groups feature

The share groups functionality will no longer be considered
experimental. The existent functional tests were modified to accomplish
with this feature graduation.

Change-Id: Ideba68c0481345e808f185195eea68e879155cf1
Partially-Implements: bp graduate-share-groups-feature
diff --git a/manila_tempest_tests/utils.py b/manila_tempest_tests/utils.py
index b22a5c1..e842a33 100644
--- a/manila_tempest_tests/utils.py
+++ b/manila_tempest_tests/utils.py
@@ -24,6 +24,7 @@
 CONF = config.CONF
 SHARE_NETWORK_SUBNETS_MICROVERSION = '2.51'
 SHARE_REPLICA_QUOTAS_MICROVERSION = "2.53"
+EXPERIMENTAL = {'X-OpenStack-Manila-API-Experimental': 'True'}
 
 
 def get_microversion_as_tuple(microversion_str):
@@ -211,3 +212,12 @@
     return next((
         subnet for subnet in share_network.get('share_network_subnets', [])
         if subnet['availability_zone'] is None), None)
+
+
+def get_extra_headers(request_version, graduation_version):
+    headers = None
+    extra_headers = False
+    if is_microversion_lt(request_version, graduation_version):
+        headers = EXPERIMENTAL
+        extra_headers = True
+    return headers, extra_headers