Rename isolated creds to dynamic creds

Renaming the isolated_creds module to dynamic_creds module, and rename
the IsolatedCreds class to DynamicCredentialProvider in preparation
to migration to tempest-lib.

Partially implements bp tempest-library

Change-Id: I78a4884e980ef7d0103639cb3792a54c69fb7761
diff --git a/tempest/scenario/utils.py b/tempest/scenario/utils.py
index 2841060..63847c3 100644
--- a/tempest/scenario/utils.py
+++ b/tempest/scenario/utils.py
@@ -104,11 +104,11 @@
             'subnet': False,
             'dhcp': False,
         }
-        self.isolated_creds = credentials.get_isolated_credentials(
+        self.cred_provider = credentials.get_credentials_provider(
             name='InputScenarioUtils',
             identity_version=CONF.identity.auth_version,
             network_resources=network_resources)
-        os = clients.Manager(self.isolated_creds.get_primary_creds())
+        os = clients.Manager(self.cred_provider.get_primary_creds())
         self.images_client = os.images_client
         self.flavors_client = os.flavors_client
         self.image_pattern = CONF.input_scenario.image_regex
@@ -120,7 +120,7 @@
         return nname
 
     def clear_creds(self):
-        self.isolated_creds.clear_isolated_creds()
+        self.cred_provider.clear_creds()
 
     @property
     def scenario_images(self):