Change cifs value from string to list for Dell manila drivers

Dell manila drivers use string as value for 'cifs' in
dhss_mandatory_security_service_association.
This fix changes it to a list.

Change-Id: I0c64e574301baf2a41a475af3b3848cbec8d495f
Closes-Bug: #1940072

manila/share/drivers/dell_emc/plugins/powermax/connection.py

@@ -86,7 +86,7 @@ class PowerMaxStorageConnection(driver.StorageConnection):
         self.ipv6_implemented = True
         self.dhss_mandatory_security_service_association = {
             'nfs': None,
-            'cifs': 'active_directory',
+            'cifs': ['active_directory', ]
         }
 
     def create_share(self, context, share, share_server=None):

manila/share/drivers/dell_emc/plugins/unity/connection.py

@@ -109,7 +109,7 @@ class UnityStorageConnection(driver.StorageConnection):
         self.driver_handles_share_servers = (True, False)
         self.dhss_mandatory_security_service_association = {
             'nfs': None,
-            'cifs': 'active_directory',
+            'cifs': ['active_directory', ]
         }
 
     def connect(self, emc_share_driver, context):

manila/share/drivers/dell_emc/plugins/vnx/connection.py

@@ -83,7 +83,7 @@ class VNXStorageConnection(driver.StorageConnection):
         self.ipv6_implemented = True
         self.dhss_mandatory_security_service_association = {
             'nfs': None,
-            'cifs': 'active_directory',
+            'cifs': ['active_directory', ]
         }
 
     def create_share(self, context, share, share_server=None):

releasenotes/notes/bug-1940072-dell-manila-fix-cifs-value-type-f65e162ee27d3e67.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Change cifs value from string to list for Dell manila drivers.
+    Fixed `bug 1940072 <https://bugs.launchpad.net/manila/+bug/1940072>`_