Change manila_tempest_tests to use credentials_factory

With the merge of 'Factor up config dependent credential classes' in tempest,
(Change-Id: I351f86f0570070105bbf24f2d904e917feea6e57)
helper methods related to credentials have been moved to
common.credentials_factory module.
manila_tempest_tests need to change accordingly.

Change-Id: I9e5c72279638e07f509a4bfe0174b5ad5ee70b45
Closes-Bug: #1519612
diff --git a/manila_tempest_tests/clients_share.py b/manila_tempest_tests/clients_share.py
index 65ee64e..023aa60 100644
--- a/manila_tempest_tests/clients_share.py
+++ b/manila_tempest_tests/clients_share.py
@@ -14,7 +14,7 @@
 #    under the License.
 
 from tempest import clients
-from tempest.common import cred_provider
+from tempest.common import credentials_factory as common_creds
 
 from manila_tempest_tests.services.share.json import shares_client
 from manila_tempest_tests.services.share.v2.json import shares_client \
@@ -22,7 +22,10 @@
 
 
 class Manager(clients.Manager):
-    def __init__(self, credentials=None, service=None):
+    def __init__(
+            self,
+            credentials=common_creds.get_configured_credentials('user'),
+            service=None):
         super(Manager, self).__init__(credentials, service)
         self.shares_client = shares_client.SharesClient(self.auth_provider)
         self.shares_v2_client = shares_v2_client.SharesV2Client(
@@ -32,11 +35,11 @@
 class AltManager(Manager):
     def __init__(self, service=None):
         super(AltManager, self).__init__(
-            cred_provider.get_configured_credentials('alt_user'), service)
+            common_creds.get_configured_credentials('alt_user'), service)
 
 
 class AdminManager(Manager):
     def __init__(self, service=None):
         super(AdminManager, self).__init__(
-            cred_provider.get_configured_credentials('identity_admin'),
+            common_creds.get_configured_credentials('identity_admin'),
             service)